diff --git a/packages/react-art/src/ReactARTHostConfig.js b/packages/react-art/src/ReactARTHostConfig.js
index 1b010e09966d5..e0e883c4b21b5 100644
--- a/packages/react-art/src/ReactARTHostConfig.js
+++ b/packages/react-art/src/ReactARTHostConfig.js
@@ -470,6 +470,28 @@ export function beforeRemoveInstance(instance) {
   // noop
 }
 
+export function isOpaqueHydratingObject(value: mixed): boolean {
+  throw new Error('Not yet implemented');
+}
+
+export function makeOpaqueHydratingObject(
+  attemptToReadValue: () => void,
+): OpaqueIDType {
+  throw new Error('Not yet implemented.');
+}
+
+export function makeClientId(): OpaqueIDType {
+  throw new Error('Not yet implemented');
+}
+
+export function makeClientIdInDEV(warnOnAccessInDEV: () => void): OpaqueIDType {
+  throw new Error('Not yet implemented');
+}
+
+export function makeServerId(): OpaqueIDType {
+  throw new Error('Not yet implemented');
+}
+
 export function registerEvent(event: any, rootContainerInstance: any) {
   throw new Error('Not yet implemented.');
 }
diff --git a/packages/react-debug-tools/src/ReactDebugHooks.js b/packages/react-debug-tools/src/ReactDebugHooks.js
index 1fab259eb1270..7b34a50394e2d 100644
--- a/packages/react-debug-tools/src/ReactDebugHooks.js
+++ b/packages/react-debug-tools/src/ReactDebugHooks.js
@@ -18,12 +18,16 @@ import type {
   ReactScopeMethods,
 } from 'shared/ReactTypes';
 import type {Fiber} from 'react-reconciler/src/ReactFiber';
+import type {OpaqueIDType} from 'react-reconciler/src/ReactFiberHostConfig';
+
 import type {Hook, TimeoutConfig} from 'react-reconciler/src/ReactFiberHooks';
 import type {Dispatcher as DispatcherType} from 'react-reconciler/src/ReactFiberHooks';
 import type {SuspenseConfig} from 'react-reconciler/src/ReactFiberSuspenseConfig';
+import {NoMode} from 'react-reconciler/src/ReactTypeOfMode';
 
 import ErrorStackParser from 'error-stack-parser';
 import ReactSharedInternals from 'shared/ReactSharedInternals';
+import {REACT_OPAQUE_ID_TYPE} from 'shared/ReactSymbols';
 import {
   FunctionComponent,
   SimpleMemoComponent,
@@ -61,6 +65,8 @@ type Dispatch<A> = A => void;
 
 let primitiveStackCache: null | Map<string, Array<any>> = null;
 
+let currentFiber: Fiber | null = null;
+
 function getPrimitiveStackCache(): Map<string, Array<any>> {
   // This initializes a cache of all primitive hooks so that the top
   // most stack frames added by calling the primitive hook can be removed.
@@ -319,6 +325,23 @@ function useDeferredValue<T>(value: T, config: TimeoutConfig | null | void): T {
   return value;
 }
 
+function useOpaqueIdentifier(): OpaqueIDType | void {
+  const hook = nextHook(); // State
+  if (currentFiber && currentFiber.mode === NoMode) {
+    nextHook(); // Effect
+  }
+  let value = hook === null ? undefined : hook.memoizedState;
+  if (value && value.$$typeof === REACT_OPAQUE_ID_TYPE) {
+    value = undefined;
+  }
+  hookLog.push({
+    primitive: 'OpaqueIdentifier',
+    stackError: new Error(),
+    value,
+  });
+  return value;
+}
+
 const Dispatcher: DispatcherType = {
   readContext,
   useCallback,
@@ -336,6 +359,7 @@ const Dispatcher: DispatcherType = {
   useMutableSource,
   useDeferredValue,
   useEvent,
+  useOpaqueIdentifier,
 };
 
 // Inspect
@@ -684,6 +708,8 @@ export function inspectHooksOfFiber(
     currentDispatcher = ReactSharedInternals.ReactCurrentDispatcher;
   }
 
+  currentFiber = fiber;
+
   if (
     fiber.tag !== FunctionComponent &&
     fiber.tag !== SimpleMemoComponent &&
diff --git a/packages/react-debug-tools/src/__tests__/ReactHooksInspectionIntegration-test.js b/packages/react-debug-tools/src/__tests__/ReactHooksInspectionIntegration-test.js
index ef41b65426f34..cca7a71dd6031 100644
--- a/packages/react-debug-tools/src/__tests__/ReactHooksInspectionIntegration-test.js
+++ b/packages/react-debug-tools/src/__tests__/ReactHooksInspectionIntegration-test.js
@@ -422,6 +422,64 @@ describe('ReactHooksInspectionIntegration', () => {
         },
       ]);
     });
+
+    it('should support composite useOpaqueIdentifier hook', () => {
+      function Foo(props) {
+        const id = React.unstable_useOpaqueIdentifier();
+        const [state] = React.useState(() => 'hello', []);
+        return <div id={id}>{state}</div>;
+      }
+
+      const renderer = ReactTestRenderer.create(<Foo />);
+      const childFiber = renderer.root.findByType(Foo)._currentFiber();
+      const tree = ReactDebugTools.inspectHooksOfFiber(childFiber);
+
+      expect(tree.length).toEqual(2);
+
+      expect(tree[0].id).toEqual(0);
+      expect(tree[0].isStateEditable).toEqual(false);
+      expect(tree[0].name).toEqual('OpaqueIdentifier');
+      expect((tree[0].value + '').startsWith('c_')).toBe(true);
+
+      expect(tree[1]).toEqual({
+        id: 1,
+        isStateEditable: true,
+        name: 'State',
+        value: 'hello',
+        subHooks: [],
+      });
+    });
+
+    it('should support composite useOpaqueIdentifier hook in concurrent mode', () => {
+      function Foo(props) {
+        const id = React.unstable_useOpaqueIdentifier();
+        const [state] = React.useState(() => 'hello', []);
+        return <div id={id}>{state}</div>;
+      }
+
+      const renderer = ReactTestRenderer.create(<Foo />, {
+        unstable_isConcurrent: true,
+      });
+      expect(Scheduler).toFlushWithoutYielding();
+
+      const childFiber = renderer.root.findByType(Foo)._currentFiber();
+      const tree = ReactDebugTools.inspectHooksOfFiber(childFiber);
+
+      expect(tree.length).toEqual(2);
+
+      expect(tree[0].id).toEqual(0);
+      expect(tree[0].isStateEditable).toEqual(false);
+      expect(tree[0].name).toEqual('OpaqueIdentifier');
+      expect((tree[0].value + '').startsWith('c_')).toBe(true);
+
+      expect(tree[1]).toEqual({
+        id: 1,
+        isStateEditable: true,
+        name: 'State',
+        value: 'hello',
+        subHooks: [],
+      });
+    });
   }
 
   describe('useDebugValue', () => {
diff --git a/packages/react-dom/src/__tests__/ReactDOMServerIntegrationHooks-test.internal.js b/packages/react-dom/src/__tests__/ReactDOMServerIntegrationHooks-test.internal.js
index 012e420f80ece..06fca95894aeb 100644
--- a/packages/react-dom/src/__tests__/ReactDOMServerIntegrationHooks-test.internal.js
+++ b/packages/react-dom/src/__tests__/ReactDOMServerIntegrationHooks-test.internal.js
@@ -18,6 +18,7 @@ let ReactFeatureFlags;
 let ReactDOM;
 let ReactDOMServer;
 let ReactTestUtils;
+let Scheduler;
 let useState;
 let useReducer;
 let useEffect;
@@ -28,6 +29,7 @@ let useRef;
 let useImperativeHandle;
 let useLayoutEffect;
 let useDebugValue;
+let useOpaqueIdentifier;
 let forwardRef;
 let yieldedValues;
 let yieldValue;
@@ -39,10 +41,12 @@ function initModules() {
 
   ReactFeatureFlags = require('shared/ReactFeatureFlags');
   ReactFeatureFlags.debugRenderPhaseSideEffectsForStrictMode = false;
+  ReactFeatureFlags.flushSuspenseFallbacksInTests = false;
   React = require('react');
   ReactDOM = require('react-dom');
   ReactDOMServer = require('react-dom/server');
   ReactTestUtils = require('react-dom/test-utils');
+  Scheduler = require('scheduler');
   useState = React.useState;
   useReducer = React.useReducer;
   useEffect = React.useEffect;
@@ -53,6 +57,7 @@ function initModules() {
   useDebugValue = React.useDebugValue;
   useImperativeHandle = React.useImperativeHandle;
   useLayoutEffect = React.useLayoutEffect;
+  useOpaqueIdentifier = React.unstable_useOpaqueIdentifier;
   forwardRef = React.forwardRef;
 
   yieldedValues = [];
@@ -78,6 +83,9 @@ const {
   itRenders,
   itThrowsWhenRendering,
   serverRender,
+  streamRender,
+  clientCleanRender,
+  clientRenderOnServerString,
 } = ReactDOMServerIntegrationUtils(initModules);
 
 describe('ReactDOMServerHooks', () => {
@@ -834,4 +842,902 @@ describe('ReactDOMServerHooks', () => {
       expect(domNode2.textContent).toEqual('42');
     });
   });
+
+  if (__EXPERIMENTAL__) {
+    describe('useOpaqueIdentifier', () => {
+      it('generates unique ids for server string render', async () => {
+        function App(props) {
+          const idOne = useOpaqueIdentifier();
+          const idTwo = useOpaqueIdentifier();
+          return (
+            <div>
+              <div aria-labelledby={idOne} />
+              <div id={idOne} />
+              <span aria-labelledby={idTwo} />
+              <span id={idTwo} />
+            </div>
+          );
+        }
+
+        const domNode = await serverRender(<App />);
+        expect(domNode.children.length).toEqual(4);
+        expect(domNode.children[0].getAttribute('aria-labelledby')).toEqual(
+          domNode.children[1].getAttribute('id'),
+        );
+        expect(domNode.children[2].getAttribute('aria-labelledby')).toEqual(
+          domNode.children[3].getAttribute('id'),
+        );
+        expect(domNode.children[0].getAttribute('aria-labelledby')).not.toEqual(
+          domNode.children[2].getAttribute('aria-labelledby'),
+        );
+        expect(
+          domNode.children[0].getAttribute('aria-labelledby'),
+        ).not.toBeNull();
+        expect(
+          domNode.children[2].getAttribute('aria-labelledby'),
+        ).not.toBeNull();
+      });
+
+      it('generates unique ids for server stream render', async () => {
+        function App(props) {
+          const idOne = useOpaqueIdentifier();
+          const idTwo = useOpaqueIdentifier();
+          return (
+            <div>
+              <div aria-labelledby={idOne} />
+              <div id={idOne} />
+              <span aria-labelledby={idTwo} />
+              <span id={idTwo} />
+            </div>
+          );
+        }
+
+        const domNode = await streamRender(<App />);
+        expect(domNode.children.length).toEqual(4);
+        expect(domNode.children[0].getAttribute('aria-labelledby')).toEqual(
+          domNode.children[1].getAttribute('id'),
+        );
+        expect(domNode.children[2].getAttribute('aria-labelledby')).toEqual(
+          domNode.children[3].getAttribute('id'),
+        );
+        expect(domNode.children[0].getAttribute('aria-labelledby')).not.toEqual(
+          domNode.children[2].getAttribute('aria-labelledby'),
+        );
+        expect(
+          domNode.children[0].getAttribute('aria-labelledby'),
+        ).not.toBeNull();
+        expect(
+          domNode.children[2].getAttribute('aria-labelledby'),
+        ).not.toBeNull();
+      });
+
+      it('generates unique ids for client render', async () => {
+        function App(props) {
+          const idOne = useOpaqueIdentifier();
+          const idTwo = useOpaqueIdentifier();
+          return (
+            <div>
+              <div aria-labelledby={idOne} />
+              <div id={idOne} />
+              <span aria-labelledby={idTwo} />
+              <span id={idTwo} />
+            </div>
+          );
+        }
+
+        const domNode = await clientCleanRender(<App />);
+        expect(domNode.children.length).toEqual(4);
+        expect(domNode.children[0].getAttribute('aria-labelledby')).toEqual(
+          domNode.children[1].getAttribute('id'),
+        );
+        expect(domNode.children[2].getAttribute('aria-labelledby')).toEqual(
+          domNode.children[3].getAttribute('id'),
+        );
+        expect(domNode.children[0].getAttribute('aria-labelledby')).not.toEqual(
+          domNode.children[2].getAttribute('aria-labelledby'),
+        );
+        expect(
+          domNode.children[0].getAttribute('aria-labelledby'),
+        ).not.toBeNull();
+        expect(
+          domNode.children[2].getAttribute('aria-labelledby'),
+        ).not.toBeNull();
+      });
+
+      it('generates unique ids for client render on good server markup', async () => {
+        function App(props) {
+          const idOne = useOpaqueIdentifier();
+          const idTwo = useOpaqueIdentifier();
+          return (
+            <div>
+              <div aria-labelledby={idOne} />
+              <div id={idOne} />
+              <span aria-labelledby={idTwo} />
+              <span id={idTwo} />
+            </div>
+          );
+        }
+
+        const domNode = await clientRenderOnServerString(<App />);
+        expect(domNode.children.length).toEqual(4);
+        expect(domNode.children[0].getAttribute('aria-labelledby')).toEqual(
+          domNode.children[1].getAttribute('id'),
+        );
+        expect(domNode.children[2].getAttribute('aria-labelledby')).toEqual(
+          domNode.children[3].getAttribute('id'),
+        );
+        expect(domNode.children[0].getAttribute('aria-labelledby')).not.toEqual(
+          domNode.children[2].getAttribute('aria-labelledby'),
+        );
+        expect(
+          domNode.children[0].getAttribute('aria-labelledby'),
+        ).not.toBeNull();
+        expect(
+          domNode.children[2].getAttribute('aria-labelledby'),
+        ).not.toBeNull();
+      });
+
+      it('useOpaqueIdentifier does not change id even if the component updates during client render', async () => {
+        let _setShowId;
+        function App() {
+          const id = useOpaqueIdentifier();
+          const [showId, setShowId] = useState(false);
+          _setShowId = setShowId;
+          return (
+            <div>
+              <div aria-labelledby={id} />
+              {showId && <div id={id} />}
+            </div>
+          );
+        }
+
+        const domNode = await clientCleanRender(<App />);
+        const oldClientId = domNode.children[0].getAttribute('aria-labelledby');
+
+        expect(domNode.children.length).toEqual(1);
+        expect(oldClientId).not.toBeNull();
+
+        await ReactTestUtils.act(async () => _setShowId(true));
+
+        expect(domNode.children.length).toEqual(2);
+        expect(domNode.children[0].getAttribute('aria-labelledby')).toEqual(
+          domNode.children[1].getAttribute('id'),
+        );
+        expect(domNode.children[0].getAttribute('aria-labelledby')).toEqual(
+          oldClientId,
+        );
+      });
+
+      it('useOpaqueIdentifier: IDs match when, after hydration, a new component that uses the ID is rendered', async () => {
+        let _setShowDiv;
+        function App() {
+          const id = useOpaqueIdentifier();
+          const [showDiv, setShowDiv] = useState(false);
+          _setShowDiv = setShowDiv;
+
+          return (
+            <div>
+              <div id={id}>Child One</div>
+              {showDiv && <div id={id}>Child Two</div>}
+            </div>
+          );
+        }
+
+        const container = document.createElement('div');
+        document.body.append(container);
+
+        container.innerHTML = ReactDOMServer.renderToString(<App />);
+        const root = ReactDOM.createRoot(container, {hydrate: true});
+        root.render(<App />);
+        Scheduler.unstable_flushAll();
+        jest.runAllTimers();
+
+        expect(container.children[0].children.length).toEqual(1);
+        const oldServerId = container.children[0].children[0].getAttribute(
+          'id',
+        );
+        expect(oldServerId).not.toBeNull();
+
+        await ReactTestUtils.act(async () => {
+          _setShowDiv(true);
+        });
+        expect(container.children[0].children.length).toEqual(2);
+        expect(container.children[0].children[0].getAttribute('id')).toEqual(
+          container.children[0].children[1].getAttribute('id'),
+        );
+        expect(
+          container.children[0].children[0].getAttribute('id'),
+        ).not.toEqual(oldServerId);
+        expect(
+          container.children[0].children[0].getAttribute('id'),
+        ).not.toBeNull();
+      });
+
+      it('useOpaqueIdentifier: IDs match when, after hydration, a new component that uses the ID is rendered for legacy', async () => {
+        let _setShowDiv;
+        function App() {
+          const id = useOpaqueIdentifier();
+          const [showDiv, setShowDiv] = useState(false);
+          _setShowDiv = setShowDiv;
+
+          return (
+            <div>
+              <div id={id}>Child One</div>
+              {showDiv && <div id={id}>Child Two</div>}
+            </div>
+          );
+        }
+
+        const container = document.createElement('div');
+        document.body.append(container);
+
+        container.innerHTML = ReactDOMServer.renderToString(<App />);
+        ReactDOM.hydrate(<App />, container);
+
+        expect(container.children[0].children.length).toEqual(1);
+        const oldServerId = container.children[0].children[0].getAttribute(
+          'id',
+        );
+        expect(oldServerId).not.toBeNull();
+
+        await ReactTestUtils.act(async () => {
+          _setShowDiv(true);
+        });
+        expect(container.children[0].children.length).toEqual(2);
+        expect(container.children[0].children[0].getAttribute('id')).toEqual(
+          container.children[0].children[1].getAttribute('id'),
+        );
+        expect(
+          container.children[0].children[0].getAttribute('id'),
+        ).not.toEqual(oldServerId);
+        expect(
+          container.children[0].children[0].getAttribute('id'),
+        ).not.toBeNull();
+      });
+
+      it('useOpaqueIdentifier: ID is not used during hydration but is used in an update', async () => {
+        let _setShow;
+        function App() {
+          Scheduler.unstable_yieldValue('App');
+          const id = useOpaqueIdentifier();
+          const [show, setShow] = useState(false);
+          _setShow = setShow;
+          return (
+            <div>
+              <span id={show ? id : null}>{'Child One'}</span>
+            </div>
+          );
+        }
+
+        const container = document.createElement('div');
+        document.body.append(container);
+        container.innerHTML = ReactDOMServer.renderToString(<App />);
+        const root = ReactDOM.createRoot(container, {hydrate: true});
+        ReactTestUtils.act(() => {
+          root.render(<App />);
+        });
+        expect(Scheduler).toHaveYielded(['App', 'App']);
+        // The ID goes from not being used to being added to the page
+        ReactTestUtils.act(() => {
+          _setShow(true);
+        });
+        expect(Scheduler).toHaveYielded(['App', 'App']);
+        expect(
+          container.getElementsByTagName('span')[0].getAttribute('id'),
+        ).not.toBeNull();
+      });
+
+      it('useOpaqueIdentifier: ID is not used during hydration but is used in an update in legacy', async () => {
+        let _setShow;
+        function App() {
+          Scheduler.unstable_yieldValue('App');
+          const id = useOpaqueIdentifier();
+          const [show, setShow] = useState(false);
+          _setShow = setShow;
+          return (
+            <div>
+              <span id={show ? id : null}>{'Child One'}</span>
+            </div>
+          );
+        }
+
+        const container = document.createElement('div');
+        document.body.append(container);
+        container.innerHTML = ReactDOMServer.renderToString(<App />);
+        ReactDOM.hydrate(<App />, container);
+        expect(Scheduler).toHaveYielded(['App', 'App']);
+        // The ID goes from not being used to being added to the page
+        ReactTestUtils.act(() => {
+          _setShow(true);
+        });
+        expect(Scheduler).toHaveYielded(['App']);
+        expect(
+          container.getElementsByTagName('span')[0].getAttribute('id'),
+        ).not.toBeNull();
+      });
+
+      it('useOpaqueIdentifierr: flushSync', async () => {
+        let _setShow;
+        function App() {
+          const id = useOpaqueIdentifier();
+          const [show, setShow] = useState(false);
+          _setShow = setShow;
+          return (
+            <div>
+              <span id={show ? id : null}>{'Child One'}</span>
+            </div>
+          );
+        }
+
+        const container = document.createElement('div');
+        document.body.append(container);
+        container.innerHTML = ReactDOMServer.renderToString(<App />);
+        const root = ReactDOM.createRoot(container, {hydrate: true});
+        ReactTestUtils.act(() => {
+          root.render(<App />);
+        });
+
+        // The ID goes from not being used to being added to the page
+        ReactTestUtils.act(() => {
+          ReactDOM.flushSync(() => {
+            _setShow(true);
+          });
+        });
+        expect(
+          container.getElementsByTagName('span')[0].getAttribute('id'),
+        ).not.toBeNull();
+      });
+
+      it('useOpaqueIdentifier: children with id hydrates before other children if ID updates', async () => {
+        let _setShow;
+
+        const child1Ref = React.createRef();
+        const childWithIDRef = React.createRef();
+        const setShowRef = React.createRef();
+
+        // RENAME THESE
+        function Child1() {
+          Scheduler.unstable_yieldValue('Child One');
+          return <span ref={child1Ref}>{'Child One'}</span>;
+        }
+
+        function Child2() {
+          Scheduler.unstable_yieldValue('Child Two');
+          return <span>{'Child Two'}</span>;
+        }
+
+        const Children = React.memo(function Children() {
+          return (
+            <React.Suspense fallback="Loading 1...">
+              <Child1 />
+              <Child2 />
+            </React.Suspense>
+          );
+        });
+
+        function ChildWithID({parentID}) {
+          Scheduler.unstable_yieldValue('Child with ID');
+          return (
+            <span id={parentID} ref={childWithIDRef}>
+              {'Child with ID'}
+            </span>
+          );
+        }
+
+        const ChildrenWithID = React.memo(function ChildrenWithID({parentID}) {
+          return (
+            <React.Suspense fallback="Loading 2...">
+              <ChildWithID parentID={parentID} />
+            </React.Suspense>
+          );
+        });
+
+        function App() {
+          const id = useOpaqueIdentifier();
+          const [show, setShow] = useState(false);
+          _setShow = setShow;
+          return (
+            <div>
+              <Children />
+              <ChildrenWithID parentID={id} />
+              {show && (
+                <span aria-labelledby={id} ref={setShowRef}>
+                  {'Child Three'}
+                </span>
+              )}
+            </div>
+          );
+        }
+
+        const container = document.createElement('div');
+        container.innerHTML = ReactDOMServer.renderToString(<App />);
+        expect(Scheduler).toHaveYielded([
+          'Child One',
+          'Child Two',
+          'Child with ID',
+        ]);
+        expect(container.textContent).toEqual(
+          'Child OneChild TwoChild with ID',
+        );
+
+        const serverId = container
+          .getElementsByTagName('span')[2]
+          .getAttribute('id');
+        expect(serverId).not.toBeNull();
+
+        const childOneSpan = container.getElementsByTagName('span')[0];
+
+        const root = ReactDOM.createRoot(container, {hydrate: true});
+        root.render(<App show={false} />);
+        expect(Scheduler).toHaveYielded([]);
+
+        //Hydrate just child one before updating state
+        expect(Scheduler).toFlushAndYieldThrough(['Child One']);
+        expect(child1Ref.current).toBe(null);
+        expect(Scheduler).toHaveYielded([]);
+
+        ReactTestUtils.act(() => {
+          _setShow(true);
+
+          // State update should trigger the ID to update, which changes the props
+          // of ChildWithID. This should cause ChildWithID to hydrate before Children
+          expect(Scheduler).toFlushAndYieldThrough([
+            'Child with ID',
+            'Child with ID',
+            'Child with ID',
+            'Child One',
+            'Child Two',
+          ]);
+
+          expect(child1Ref.current).toBe(null);
+          expect(childWithIDRef.current).toEqual(
+            container.getElementsByTagName('span')[2],
+          );
+
+          expect(setShowRef.current).toEqual(
+            container.getElementsByTagName('span')[3],
+          );
+
+          expect(childWithIDRef.current.getAttribute('id')).toEqual(
+            setShowRef.current.getAttribute('aria-labelledby'),
+          );
+          expect(childWithIDRef.current.getAttribute('id')).not.toEqual(
+            serverId,
+          );
+        });
+
+        // Children hydrates after ChildWithID
+        expect(child1Ref.current).toBe(childOneSpan);
+
+        Scheduler.unstable_flushAll();
+
+        expect(Scheduler).toHaveYielded([]);
+      });
+
+      it('useOpaqueIdentifier: IDs match when part of the DOM tree is server rendered and part is client rendered', async () => {
+        let suspend = true;
+        let resolve;
+        const promise = new Promise(
+          resolvePromise => (resolve = resolvePromise),
+        );
+
+        function Child({text}) {
+          if (suspend) {
+            throw promise;
+          } else {
+            return text;
+          }
+        }
+
+        function RenderedChild() {
+          useEffect(() => {
+            Scheduler.unstable_yieldValue('Child did commit');
+          });
+          return null;
+        }
+
+        function App() {
+          const id = useOpaqueIdentifier();
+          useEffect(() => {
+            Scheduler.unstable_yieldValue('Did commit');
+          });
+          return (
+            <div>
+              <div id={id}>Child One</div>
+              <RenderedChild />
+              <React.Suspense fallback={'Fallback'}>
+                <div id={id}>
+                  <Child text="Child Two" />
+                </div>
+              </React.Suspense>
+            </div>
+          );
+        }
+
+        const container = document.createElement('div');
+        document.body.appendChild(container);
+
+        container.innerHTML = ReactDOMServer.renderToString(<App />);
+
+        suspend = true;
+        const root = ReactDOM.createRoot(container, {hydrate: true});
+        await ReactTestUtils.act(async () => {
+          root.render(<App />);
+        });
+        jest.runAllTimers();
+        expect(Scheduler).toHaveYielded(['Child did commit', 'Did commit']);
+        expect(Scheduler).toFlushAndYield([]);
+
+        const serverId = container.children[0].children[0].getAttribute('id');
+        expect(container.children[0].children.length).toEqual(1);
+        expect(
+          container.children[0].children[0].getAttribute('id'),
+        ).not.toBeNull();
+
+        await ReactTestUtils.act(async () => {
+          suspend = false;
+          resolve();
+          await promise;
+        });
+
+        expect(Scheduler).toHaveYielded(['Child did commit', 'Did commit']);
+        expect(Scheduler).toFlushAndYield([]);
+        jest.runAllTimers();
+
+        expect(container.children[0].children.length).toEqual(2);
+        expect(container.children[0].children[0].getAttribute('id')).toEqual(
+          container.children[0].children[1].getAttribute('id'),
+        );
+        expect(
+          container.children[0].children[0].getAttribute('id'),
+        ).not.toEqual(serverId);
+        expect(
+          container.children[0].children[0].getAttribute('id'),
+        ).not.toBeNull();
+      });
+
+      it('useOpaqueIdentifier warn when there is a hydration error', async () => {
+        function Child({appId}) {
+          return <div aria-labelledby={appId} />;
+        }
+        function App() {
+          const id = useOpaqueIdentifier();
+          return <Child appId={id} />;
+        }
+
+        const container = document.createElement('div');
+        document.body.appendChild(container);
+
+        // This is the wrong HTML string
+        container.innerHTML = '<span></span>';
+        ReactDOM.createRoot(container, {hydrate: true}).render(<App />);
+        expect(() =>
+          expect(() => Scheduler.unstable_flushAll()).toThrow(),
+        ).toErrorDev([
+          'Warning: Expected server HTML to contain a matching <div> in <div>.',
+        ]);
+      });
+
+      it('useOpaqueIdentifier: IDs match when part of the DOM tree is server rendered and part is client rendered', async () => {
+        let suspend = true;
+
+        function Child({text}) {
+          if (suspend) {
+            throw new Promise(() => {});
+          } else {
+            return text;
+          }
+        }
+
+        function RenderedChild() {
+          useEffect(() => {
+            Scheduler.unstable_yieldValue('Child did commit');
+          });
+          return null;
+        }
+
+        function App() {
+          const id = useOpaqueIdentifier();
+          useEffect(() => {
+            Scheduler.unstable_yieldValue('Did commit');
+          });
+          return (
+            <div>
+              <div id={id}>Child One</div>
+              <RenderedChild />
+              <React.Suspense fallback={'Fallback'}>
+                <div id={id}>
+                  <Child text="Child Two" />
+                </div>
+              </React.Suspense>
+            </div>
+          );
+        }
+
+        const container = document.createElement('div');
+        document.body.appendChild(container);
+
+        container.innerHTML = ReactDOMServer.renderToString(<App />);
+
+        suspend = false;
+        const root = ReactDOM.createRoot(container, {hydrate: true});
+        await ReactTestUtils.act(async () => {
+          root.render(<App />);
+        });
+        jest.runAllTimers();
+        expect(Scheduler).toHaveYielded([
+          'Child did commit',
+          'Did commit',
+          'Child did commit',
+          'Did commit',
+        ]);
+        expect(Scheduler).toFlushAndYield([]);
+
+        expect(container.children[0].children.length).toEqual(2);
+        expect(container.children[0].children[0].getAttribute('id')).toEqual(
+          container.children[0].children[1].getAttribute('id'),
+        );
+        expect(
+          container.children[0].children[0].getAttribute('id'),
+        ).not.toBeNull();
+      });
+
+      it('useOpaqueIdentifier warn when there is a hydration error', async () => {
+        function Child({appId}) {
+          return <div aria-labelledby={appId} />;
+        }
+        function App() {
+          const id = useOpaqueIdentifier();
+          return <Child appId={id} />;
+        }
+
+        const container = document.createElement('div');
+        document.body.appendChild(container);
+
+        // This is the wrong HTML string
+        container.innerHTML = '<span></span>';
+        ReactDOM.createRoot(container, {hydrate: true}).render(<App />);
+        expect(() =>
+          expect(() => Scheduler.unstable_flushAll()).toThrow(),
+        ).toErrorDev([
+          'Warning: Expected server HTML to contain a matching <div> in <div>.',
+        ]);
+      });
+
+      it('useOpaqueIdentifier throws when there is a hydration error and we are using ID as a string', async () => {
+        function Child({appId}) {
+          return <div aria-labelledby={appId + ''} />;
+        }
+        function App() {
+          const id = useOpaqueIdentifier();
+          return <Child appId={id} />;
+        }
+
+        const container = document.createElement('div');
+        document.body.appendChild(container);
+
+        // This is the wrong HTML string
+        container.innerHTML = '<span></span>';
+        ReactDOM.createRoot(container, {hydrate: true}).render(<App />);
+        expect(() =>
+          expect(() => Scheduler.unstable_flushAll()).toThrow(
+            'The object passed back from useOpaqueIdentifier is meant to be passed through to attributes only. ' +
+              'Do not read the value directly.',
+          ),
+        ).toErrorDev(
+          [
+            'Warning: The object passed back from useOpaqueIdentifier is meant to be passed through to attributes only. Do not read the value directly.',
+            'Warning: Did not expect server HTML to contain a <span> in <div>.',
+          ],
+          {withoutStack: 1},
+        );
+      });
+
+      it('useOpaqueIdentifier throws when there is a hydration error and we are using ID as a string', async () => {
+        function Child({appId}) {
+          return <div aria-labelledby={appId + ''} />;
+        }
+        function App() {
+          const id = useOpaqueIdentifier();
+          return <Child appId={id} />;
+        }
+
+        const container = document.createElement('div');
+        document.body.appendChild(container);
+
+        // This is the wrong HTML string
+        container.innerHTML = '<span></span>';
+        ReactDOM.createRoot(container, {hydrate: true}).render(<App />);
+        expect(() =>
+          expect(() => Scheduler.unstable_flushAll()).toThrow(
+            'The object passed back from useOpaqueIdentifier is meant to be passed through to attributes only. ' +
+              'Do not read the value directly.',
+          ),
+        ).toErrorDev(
+          [
+            'Warning: The object passed back from useOpaqueIdentifier is meant to be passed through to attributes only. Do not read the value directly.',
+            'Warning: Did not expect server HTML to contain a <span> in <div>.',
+          ],
+          {withoutStack: 1},
+        );
+      });
+
+      it('useOpaqueIdentifier throws if you try to use the result as a string in a child component', async () => {
+        function Child({appId}) {
+          return <div aria-labelledby={appId + ''} />;
+        }
+        function App() {
+          const id = useOpaqueIdentifier();
+          return <Child appId={id} />;
+        }
+
+        const container = document.createElement('div');
+        document.body.appendChild(container);
+
+        container.innerHTML = ReactDOMServer.renderToString(<App />);
+        ReactDOM.createRoot(container, {hydrate: true}).render(<App />);
+        expect(() =>
+          expect(() => Scheduler.unstable_flushAll()).toThrow(
+            'The object passed back from useOpaqueIdentifier is meant to be passed through to attributes only. ' +
+              'Do not read the value directly.',
+          ),
+        ).toErrorDev(
+          [
+            'Warning: The object passed back from useOpaqueIdentifier is meant to be passed through to attributes only. Do not read the value directly.',
+            'Warning: Did not expect server HTML to contain a <div> in <div>.',
+          ],
+          {withoutStack: 1},
+        );
+      });
+
+      it('useOpaqueIdentifier throws if you try to use the result as a string', async () => {
+        function App() {
+          const id = useOpaqueIdentifier();
+          return <div aria-labelledby={id + ''} />;
+        }
+
+        const container = document.createElement('div');
+        document.body.appendChild(container);
+
+        container.innerHTML = ReactDOMServer.renderToString(<App />);
+        ReactDOM.createRoot(container, {hydrate: true}).render(<App />);
+        expect(() =>
+          expect(() => Scheduler.unstable_flushAll()).toThrow(
+            'The object passed back from useOpaqueIdentifier is meant to be passed through to attributes only. ' +
+              'Do not read the value directly.',
+          ),
+        ).toErrorDev(
+          [
+            'Warning: The object passed back from useOpaqueIdentifier is meant to be passed through to attributes only. Do not read the value directly.',
+            'Warning: Did not expect server HTML to contain a <div> in <div>.',
+          ],
+          {withoutStack: 1},
+        );
+      });
+
+      it('useOpaqueIdentifier throws if you try to use the result as a string in a child component wrapped in a Suspense', async () => {
+        function Child({appId}) {
+          return <div aria-labelledby={appId + ''} />;
+        }
+        function App() {
+          const id = useOpaqueIdentifier();
+          return (
+            <React.Suspense fallback={null}>
+              <Child appId={id} />
+            </React.Suspense>
+          );
+        }
+
+        const container = document.createElement('div');
+        document.body.appendChild(container);
+
+        container.innerHTML = ReactDOMServer.renderToString(<App />);
+
+        ReactDOM.createRoot(container, {hydrate: true}).render(<App />);
+
+        expect(() =>
+          expect(() => Scheduler.unstable_flushAll()).toThrow(
+            'The object passed back from useOpaqueIdentifier is meant to be passed through to attributes only. ' +
+              'Do not read the value directly.',
+          ),
+        ).toErrorDev([
+          'The object passed back from useOpaqueIdentifier is meant to be passed through to attributes only. ' +
+            'Do not read the value directly.',
+        ]);
+      });
+
+      it('useOpaqueIdentifier throws if you try to add the result as a number in a child component wrapped in a Suspense', async () => {
+        function Child({appId}) {
+          return <div aria-labelledby={+appId} />;
+        }
+        function App() {
+          const [show] = useState(false);
+          const id = useOpaqueIdentifier();
+          return (
+            <React.Suspense fallback={null}>
+              {show && <div id={id} />}
+              <Child appId={id} />
+            </React.Suspense>
+          );
+        }
+
+        const container = document.createElement('div');
+        document.body.appendChild(container);
+
+        container.innerHTML = ReactDOMServer.renderToString(<App />);
+
+        ReactDOM.createRoot(container, {hydrate: true}).render(<App />);
+
+        expect(() =>
+          expect(() => Scheduler.unstable_flushAll()).toThrow(
+            'The object passed back from useOpaqueIdentifier is meant to be passed through to attributes only. ' +
+              'Do not read the value directly.',
+          ),
+        ).toErrorDev([
+          'The object passed back from useOpaqueIdentifier is meant to be passed through to attributes only. ' +
+            'Do not read the value directly.',
+        ]);
+      });
+
+      it('useOpaqueIdentifier with two opaque identifiers on the same page', () => {
+        let _setShow;
+
+        function App() {
+          const id1 = useOpaqueIdentifier();
+          const id2 = useOpaqueIdentifier();
+          const [show, setShow] = useState(true);
+          _setShow = setShow;
+
+          return (
+            <div>
+              <React.Suspense fallback={null}>
+                {show ? (
+                  <span id={id1}>{'Child'}</span>
+                ) : (
+                  <span id={id2}>{'Child'}</span>
+                )}
+              </React.Suspense>
+              <span aria-labelledby={id1}>{'test'}</span>
+            </div>
+          );
+        }
+
+        const container = document.createElement('div');
+        document.body.appendChild(container);
+
+        container.innerHTML = ReactDOMServer.renderToString(<App />);
+
+        const serverID = container
+          .getElementsByTagName('span')[0]
+          .getAttribute('id');
+        expect(serverID).not.toBeNull();
+        expect(
+          container
+            .getElementsByTagName('span')[1]
+            .getAttribute('aria-labelledby'),
+        ).toEqual(serverID);
+
+        ReactDOM.createRoot(container, {hydrate: true}).render(<App />);
+        jest.runAllTimers();
+        expect(Scheduler).toHaveYielded([]);
+        expect(Scheduler).toFlushAndYield([]);
+
+        ReactTestUtils.act(() => {
+          _setShow(false);
+        });
+
+        expect(
+          container
+            .getElementsByTagName('span')[1]
+            .getAttribute('aria-labelledby'),
+        ).toEqual(serverID);
+        expect(
+          container.getElementsByTagName('span')[0].getAttribute('id'),
+        ).not.toEqual(serverID);
+        expect(
+          container.getElementsByTagName('span')[0].getAttribute('id'),
+        ).not.toBeNull();
+      });
+    });
+  }
 });
diff --git a/packages/react-dom/src/client/DOMPropertyOperations.js b/packages/react-dom/src/client/DOMPropertyOperations.js
index 2fcf3d2efc37f..2dcb1ace8ab9f 100644
--- a/packages/react-dom/src/client/DOMPropertyOperations.js
+++ b/packages/react-dom/src/client/DOMPropertyOperations.js
@@ -20,6 +20,7 @@ import {
   disableJavaScriptURLs,
   enableTrustedTypesIntegration,
 } from 'shared/ReactFeatureFlags';
+import {isOpaqueHydratingObject} from './ReactDOMHostConfig';
 
 import type {PropertyInfo} from '../shared/DOMProperty';
 
@@ -107,6 +108,13 @@ export function getValueForAttribute(
     if (!isAttributeNameSafe(name)) {
       return;
     }
+
+    // If the object is an opaque reference ID, it's expected that
+    // the next prop is different than the server value, so just return
+    // expected
+    if (isOpaqueHydratingObject(expected)) {
+      return expected;
+    }
     if (!node.hasAttribute(name)) {
       return expected === undefined ? undefined : null;
     }
diff --git a/packages/react-dom/src/client/ReactDOMComponent.js b/packages/react-dom/src/client/ReactDOMComponent.js
index e8a0396e24a33..2f0190084ba5d 100644
--- a/packages/react-dom/src/client/ReactDOMComponent.js
+++ b/packages/react-dom/src/client/ReactDOMComponent.js
@@ -84,6 +84,7 @@ import possibleStandardNames from '../shared/possibleStandardNames';
 import {validateProperties as validateARIAProperties} from '../shared/ReactDOMInvalidARIAHook';
 import {validateProperties as validateInputProperties} from '../shared/ReactDOMNullInputValuePropHook';
 import {validateProperties as validateUnknownProperties} from '../shared/ReactDOMUnknownPropertyHook';
+import {REACT_OPAQUE_ID_TYPE} from 'shared/ReactSymbols';
 
 import {
   enableDeprecatedFlareAPI,
@@ -849,6 +850,15 @@ export function diffProperties(
         // to update this element.
         updatePayload = [];
       }
+    } else if (
+      typeof nextProp === 'object' &&
+      nextProp !== null &&
+      nextProp.$$typeof === REACT_OPAQUE_ID_TYPE
+    ) {
+      // If we encounter useOpaqueReference's opaque object, this means we are hydrating.
+      // In this case, call the opaque object's toString function which generates a new client
+      // ID so client and server IDs match and throws to rerender.
+      nextProp.toString();
     } else {
       // For any other property we always add it to the queue and then we
       // filter it out using the whitelist during the commit.
diff --git a/packages/react-dom/src/client/ReactDOMHostConfig.js b/packages/react-dom/src/client/ReactDOMHostConfig.js
index 05b6f50ebeb73..b8b0050de7a59 100644
--- a/packages/react-dom/src/client/ReactDOMHostConfig.js
+++ b/packages/react-dom/src/client/ReactDOMHostConfig.js
@@ -58,6 +58,7 @@ import {
 } from '../shared/HTMLNodeType';
 import dangerousStyleValue from '../shared/dangerousStyleValue';
 
+import {REACT_OPAQUE_ID_TYPE} from 'shared/ReactSymbols';
 import {
   mountEventResponder,
   unmountEventResponder,
@@ -150,6 +151,13 @@ export type TimeoutHandle = TimeoutID;
 export type NoTimeout = -1;
 export type RendererInspectionConfig = $ReadOnly<{||}>;
 
+export opaque type OpaqueIDType =
+  | string
+  | {
+      toString: () => string | void,
+      valueOf: () => string | void,
+    };
+
 type SelectionInformation = {|
   activeElementDetached: null | HTMLElement,
   focusedElem: null | HTMLElement,
@@ -1147,6 +1155,48 @@ export function getInstanceFromNode(node: HTMLElement): null | Object {
   return getClosestInstanceFromNode(node) || null;
 }
 
+let clientId: number = 0;
+export function makeClientId(): OpaqueIDType {
+  return 'r:' + (clientId++).toString(36);
+}
+
+export function makeClientIdInDEV(warnOnAccessInDEV: () => void): OpaqueIDType {
+  const id = 'r:' + (clientId++).toString(36);
+  return {
+    toString() {
+      warnOnAccessInDEV();
+      return id;
+    },
+    valueOf() {
+      warnOnAccessInDEV();
+      return id;
+    },
+  };
+}
+
+let serverId: number = 0;
+export function makeServerId(): OpaqueIDType {
+  return 'R:' + (serverId++).toString(36);
+}
+
+export function isOpaqueHydratingObject(value: mixed): boolean {
+  return (
+    value !== null &&
+    typeof value === 'object' &&
+    value.$$typeof === REACT_OPAQUE_ID_TYPE
+  );
+}
+
+export function makeOpaqueHydratingObject(
+  attemptToReadValue: () => void,
+): OpaqueIDType {
+  return {
+    $$typeof: REACT_OPAQUE_ID_TYPE,
+    toString: attemptToReadValue,
+    valueOf: attemptToReadValue,
+  };
+}
+
 export function registerEvent(
   event: ReactDOMListenerEvent,
   rootContainerInstance: Container,
diff --git a/packages/react-dom/src/server/ReactPartialRendererHooks.js b/packages/react-dom/src/server/ReactPartialRendererHooks.js
index 963c025bb7bcf..0ccbf9f41e776 100644
--- a/packages/react-dom/src/server/ReactPartialRendererHooks.js
+++ b/packages/react-dom/src/server/ReactPartialRendererHooks.js
@@ -12,6 +12,8 @@ import type {
   TimeoutConfig,
 } from 'react-reconciler/src/ReactFiberHooks';
 import type {ThreadID} from './ReactThreadIDAllocator';
+import type {OpaqueIDType} from 'react-reconciler/src/ReactFiberHostConfig';
+
 import type {
   MutableSource,
   MutableSourceGetSnapshotFn,
@@ -23,6 +25,7 @@ import type {SuspenseConfig} from 'react-reconciler/src/ReactFiberSuspenseConfig
 import type {ReactDOMListenerMap} from '../shared/ReactDOMTypes';
 
 import {validateContextBounds} from './ReactPartialRendererContext';
+import {makeServerId} from '../client/ReactDOMHostConfig';
 
 import invariant from 'shared/invariant';
 import is from 'shared/objectIs';
@@ -491,6 +494,10 @@ function useTransition(
   return [startTransition, false];
 }
 
+function useOpaqueIdentifier(): OpaqueIDType {
+  return makeServerId();
+}
+
 function useEvent(event: any): ReactDOMListenerMap {
   return {
     clear: noop,
@@ -525,6 +532,7 @@ export const Dispatcher: DispatcherType = {
   useDeferredValue,
   useTransition,
   useEvent,
+  useOpaqueIdentifier,
   // Subscriptions are not setup in a server environment.
   useMutableSource,
 };
diff --git a/packages/react-native-renderer/src/ReactFabricHostConfig.js b/packages/react-native-renderer/src/ReactFabricHostConfig.js
index cd77692132cc5..91aa98398114e 100644
--- a/packages/react-native-renderer/src/ReactFabricHostConfig.js
+++ b/packages/react-native-renderer/src/ReactFabricHostConfig.js
@@ -80,6 +80,7 @@ export type NoTimeout = -1;
 export type ReactListenerEvent = Object;
 export type ReactListenerMap = Object;
 export type ReactListener = Object;
+export type OpaqueIDType = void;
 
 export type RendererInspectionConfig = $ReadOnly<{|
   // Deprecated. Replaced with getInspectorDataForViewAtPoint.
@@ -486,6 +487,28 @@ export function beforeRemoveInstance(instance: any) {
   // noop
 }
 
+export function isOpaqueHydratingObject(value: mixed): boolean {
+  throw new Error('Not yet implemented');
+}
+
+export function makeOpaqueHydratingObject(
+  attemptToReadValue: () => void,
+): OpaqueIDType {
+  throw new Error('Not yet implemented.');
+}
+
+export function makeClientId(): OpaqueIDType {
+  throw new Error('Not yet implemented');
+}
+
+export function makeClientIdInDEV(warnOnAccessInDEV: () => void): OpaqueIDType {
+  throw new Error('Not yet implemented');
+}
+
+export function makeServerId(): OpaqueIDType {
+  throw new Error('Not yet implemented');
+}
+
 export function registerEvent(event: any, rootContainerInstance: Container) {
   throw new Error('Not yet implemented.');
 }
diff --git a/packages/react-native-renderer/src/ReactNativeHostConfig.js b/packages/react-native-renderer/src/ReactNativeHostConfig.js
index 990c4d2123a3f..a6ed4de72c392 100644
--- a/packages/react-native-renderer/src/ReactNativeHostConfig.js
+++ b/packages/react-native-renderer/src/ReactNativeHostConfig.js
@@ -47,6 +47,7 @@ export type ChildSet = void; // Unused
 
 export type TimeoutHandle = TimeoutID;
 export type NoTimeout = -1;
+export type OpaqueIDType = void;
 
 export type RendererInspectionConfig = $ReadOnly<{|
   // Deprecated. Replaced with getInspectorDataForViewAtPoint.
@@ -535,6 +536,28 @@ export function beforeRemoveInstance(instance: any) {
   // noop
 }
 
+export function isOpaqueHydratingObject(value: mixed): boolean {
+  throw new Error('Not yet implemented');
+}
+
+export function makeOpaqueHydratingObject(
+  attemptToReadValue: () => void,
+): OpaqueIDType {
+  throw new Error('Not yet implemented.');
+}
+
+export function makeClientId(): OpaqueIDType {
+  throw new Error('Not yet implemented');
+}
+
+export function makeClientIdInDEV(warnOnAccessInDEV: () => void): OpaqueIDType {
+  throw new Error('Not yet implemented');
+}
+
+export function makeServerId(): OpaqueIDType {
+  throw new Error('Not yet implemented');
+}
+
 export function registerEvent(event: any, rootContainerInstance: Container) {
   throw new Error('Not yet implemented.');
 }
diff --git a/packages/react-reconciler/src/ReactCurrentFiber.js b/packages/react-reconciler/src/ReactCurrentFiber.js
index 617dd1ff87f3a..dfdf67e692b0e 100644
--- a/packages/react-reconciler/src/ReactCurrentFiber.js
+++ b/packages/react-reconciler/src/ReactCurrentFiber.js
@@ -103,3 +103,9 @@ export function setIsRendering(rendering: boolean) {
     isRendering = rendering;
   }
 }
+
+export function getIsRendering() {
+  if (__DEV__) {
+    return isRendering;
+  }
+}
diff --git a/packages/react-reconciler/src/ReactFiberHooks.js b/packages/react-reconciler/src/ReactFiberHooks.js
index 5803115705425..81514012002e7 100644
--- a/packages/react-reconciler/src/ReactFiberHooks.js
+++ b/packages/react-reconciler/src/ReactFiberHooks.js
@@ -23,6 +23,7 @@ import type {SuspenseConfig} from './ReactFiberSuspenseConfig';
 import type {ReactPriorityLevel} from './SchedulerWithReactIntegration';
 import type {FiberRoot} from './ReactFiberRoot';
 import type {
+  OpaqueIDType,
   ReactListenerEvent,
   ReactListenerMap,
   ReactListener,
@@ -33,6 +34,7 @@ import {enableUseEventAPI} from 'shared/ReactFeatureFlags';
 
 import {markRootExpiredAtTime} from './ReactFiberRoot';
 import {NoWork, Sync} from './ReactFiberExpirationTime';
+import {NoMode, BlockingMode} from './ReactTypeOfMode';
 import {readContext} from './ReactFiberNewContext';
 import {createDeprecatedResponderListener} from './ReactFiberDeprecatedEvents';
 import {
@@ -74,6 +76,12 @@ import {
   runWithPriority,
   getCurrentPriorityLevel,
 } from './SchedulerWithReactIntegration';
+import {getIsHydrating} from './ReactFiberHydrationContext';
+import {
+  makeClientId,
+  makeClientIdInDEV,
+  makeOpaqueHydratingObject,
+} from './ReactFiberHostConfig';
 import {
   getLastPendingExpirationTime,
   getWorkInProgressVersion,
@@ -83,6 +91,7 @@ import {
   warnAboutMultipleRenderersDEV,
 } from './ReactMutableSource';
 import {getRootHostContainer} from './ReactFiberHostContext';
+import {getIsRendering} from './ReactCurrentFiber';
 
 const {ReactCurrentDispatcher, ReactCurrentBatchConfig} = ReactSharedInternals;
 
@@ -132,6 +141,7 @@ export type Dispatcher = {|
     subscribe: MutableSourceSubscribeFn<Source, Snapshot>,
   ): Snapshot,
   useEvent(event: ReactListenerEvent): ReactListenerMap,
+  useOpaqueIdentifier(): OpaqueIDType | void,
 |};
 
 type Update<S, A> = {|
@@ -166,10 +176,13 @@ export type HookType =
   | 'useDeferredValue'
   | 'useTransition'
   | 'useMutableSource'
-  | 'useEvent';
+  | 'useEvent'
+  | 'useOpaqueIdentifier';
 
 let didWarnAboutMismatchedHooksForComponent;
+let didWarnAboutUseOpaqueIdentifier;
 if (__DEV__) {
+  didWarnAboutUseOpaqueIdentifier = {};
   didWarnAboutMismatchedHooksForComponent = new Set();
 }
 
@@ -564,6 +577,8 @@ export function resetHooksAfterThrow(): void {
     hookTypesUpdateIndexDev = -1;
 
     currentHookNameInDev = null;
+
+    isUpdatingOpaqueValueInRenderPhase = false;
   }
 
   didScheduleRenderPhaseUpdate = false;
@@ -1569,6 +1584,93 @@ function rerenderTransition(
   return [start, isPending];
 }
 
+let isUpdatingOpaqueValueInRenderPhase = false;
+export function getIsUpdatingOpaqueValueInRenderPhaseInDEV(): boolean | void {
+  if (__DEV__) {
+    return isUpdatingOpaqueValueInRenderPhase;
+  }
+}
+
+function warnOnOpaqueIdentifierAccessInDEV(fiber) {
+  if (__DEV__) {
+    // TODO: Should warn in effects and callbacks, too
+    const name = getComponentName(fiber.type) || 'Unknown';
+    if (getIsRendering() && !didWarnAboutUseOpaqueIdentifier[name]) {
+      console.error(
+        'The object passed back from useOpaqueIdentifier is meant to be ' +
+          'passed through to attributes only. Do not read the ' +
+          'value directly.',
+      );
+      didWarnAboutUseOpaqueIdentifier[name] = true;
+    }
+  }
+}
+
+function mountOpaqueIdentifier(): OpaqueIDType | void {
+  const makeId = __DEV__
+    ? makeClientIdInDEV.bind(
+        null,
+        warnOnOpaqueIdentifierAccessInDEV.bind(null, currentlyRenderingFiber),
+      )
+    : makeClientId;
+
+  if (getIsHydrating()) {
+    let didUpgrade = false;
+    const fiber = currentlyRenderingFiber;
+    const readValue = () => {
+      if (!didUpgrade) {
+        // Only upgrade once. This works even inside the render phase because
+        // the update is added to a shared queue, which outlasts the
+        // in-progress render.
+        didUpgrade = true;
+        if (__DEV__) {
+          isUpdatingOpaqueValueInRenderPhase = true;
+          setId(makeId());
+          isUpdatingOpaqueValueInRenderPhase = false;
+          warnOnOpaqueIdentifierAccessInDEV(fiber);
+        } else {
+          setId(makeId());
+        }
+      }
+      invariant(
+        false,
+        'The object passed back from useOpaqueIdentifier is meant to be ' +
+          'passed through to attributes only. Do not read the value directly.',
+      );
+    };
+    const id = makeOpaqueHydratingObject(readValue);
+
+    const setId = mountState(id)[1];
+
+    if ((currentlyRenderingFiber.mode & BlockingMode) === NoMode) {
+      currentlyRenderingFiber.effectTag |= UpdateEffect | PassiveEffect;
+      pushEffect(
+        HookHasEffect | HookPassive,
+        () => {
+          setId(makeId());
+        },
+        undefined,
+        null,
+      );
+    }
+    return id;
+  } else {
+    const id = makeId();
+    mountState(id);
+    return id;
+  }
+}
+
+function updateOpaqueIdentifier(): OpaqueIDType | void {
+  const id = updateState(undefined)[0];
+  return id;
+}
+
+function rerenderOpaqueIdentifier(): OpaqueIDType | void {
+  const id = rerenderState(undefined)[0];
+  return id;
+}
+
 function dispatchAction<S, A>(
   fiber: Fiber,
   queue: UpdateQueue<S, A>,
@@ -1848,6 +1950,7 @@ export const ContextOnlyDispatcher: Dispatcher = {
   useTransition: throwInvalidHookError,
   useMutableSource: throwInvalidHookError,
   useEvent: throwInvalidHookError,
+  useOpaqueIdentifier: throwInvalidHookError,
 };
 
 const HooksDispatcherOnMount: Dispatcher = {
@@ -1868,6 +1971,7 @@ const HooksDispatcherOnMount: Dispatcher = {
   useTransition: mountTransition,
   useMutableSource: mountMutableSource,
   useEvent: mountEventListener,
+  useOpaqueIdentifier: mountOpaqueIdentifier,
 };
 
 const HooksDispatcherOnUpdate: Dispatcher = {
@@ -1888,6 +1992,7 @@ const HooksDispatcherOnUpdate: Dispatcher = {
   useTransition: updateTransition,
   useMutableSource: updateMutableSource,
   useEvent: updateEventListener,
+  useOpaqueIdentifier: updateOpaqueIdentifier,
 };
 
 const HooksDispatcherOnRerender: Dispatcher = {
@@ -1908,6 +2013,7 @@ const HooksDispatcherOnRerender: Dispatcher = {
   useTransition: rerenderTransition,
   useMutableSource: updateMutableSource,
   useEvent: updateEventListener,
+  useOpaqueIdentifier: rerenderOpaqueIdentifier,
 };
 
 let HooksDispatcherOnMountInDEV: Dispatcher | null = null;
@@ -1944,7 +2050,6 @@ if (__DEV__) {
     ): T {
       return readContext(context, observedBits);
     },
-
     useCallback<T>(callback: T, deps: Array<mixed> | void | null): T {
       currentHookNameInDev = 'useCallback';
       mountHookTypesDev();
@@ -2071,6 +2176,11 @@ if (__DEV__) {
       mountHookTypesDev();
       return mountEventListener(event);
     },
+    useOpaqueIdentifier(): OpaqueIDType | void {
+      currentHookNameInDev = 'useOpaqueIdentifier';
+      mountHookTypesDev();
+      return mountOpaqueIdentifier();
+    },
   };
 
   HooksDispatcherOnMountWithHookTypesInDEV = {
@@ -2080,7 +2190,6 @@ if (__DEV__) {
     ): T {
       return readContext(context, observedBits);
     },
-
     useCallback<T>(callback: T, deps: Array<mixed> | void | null): T {
       currentHookNameInDev = 'useCallback';
       updateHookTypesDev();
@@ -2202,6 +2311,11 @@ if (__DEV__) {
       updateHookTypesDev();
       return mountEventListener(event);
     },
+    useOpaqueIdentifier(): OpaqueIDType | void {
+      currentHookNameInDev = 'useOpaqueIdentifier';
+      updateHookTypesDev();
+      return mountOpaqueIdentifier();
+    },
   };
 
   HooksDispatcherOnUpdateInDEV = {
@@ -2211,7 +2325,6 @@ if (__DEV__) {
     ): T {
       return readContext(context, observedBits);
     },
-
     useCallback<T>(callback: T, deps: Array<mixed> | void | null): T {
       currentHookNameInDev = 'useCallback';
       updateHookTypesDev();
@@ -2333,6 +2446,11 @@ if (__DEV__) {
       updateHookTypesDev();
       return updateEventListener(event);
     },
+    useOpaqueIdentifier(): OpaqueIDType | void {
+      currentHookNameInDev = 'useOpaqueIdentifier';
+      updateHookTypesDev();
+      return updateOpaqueIdentifier();
+    },
   };
 
   HooksDispatcherOnRerenderInDEV = {
@@ -2464,6 +2582,11 @@ if (__DEV__) {
       updateHookTypesDev();
       return updateEventListener(event);
     },
+    useOpaqueIdentifier(): OpaqueIDType | void {
+      currentHookNameInDev = 'useOpaqueIdentifier';
+      updateHookTypesDev();
+      return rerenderOpaqueIdentifier();
+    },
   };
 
   InvalidNestedHooksDispatcherOnMountInDEV = {
@@ -2474,7 +2597,6 @@ if (__DEV__) {
       warnInvalidContextAccess();
       return readContext(context, observedBits);
     },
-
     useCallback<T>(callback: T, deps: Array<mixed> | void | null): T {
       currentHookNameInDev = 'useCallback';
       warnInvalidHookAccess();
@@ -2611,6 +2733,12 @@ if (__DEV__) {
       mountHookTypesDev();
       return mountEventListener(event);
     },
+    useOpaqueIdentifier(): OpaqueIDType | void {
+      currentHookNameInDev = 'useOpaqueIdentifier';
+      warnInvalidHookAccess();
+      mountHookTypesDev();
+      return mountOpaqueIdentifier();
+    },
   };
 
   InvalidNestedHooksDispatcherOnUpdateInDEV = {
@@ -2621,7 +2749,6 @@ if (__DEV__) {
       warnInvalidContextAccess();
       return readContext(context, observedBits);
     },
-
     useCallback<T>(callback: T, deps: Array<mixed> | void | null): T {
       currentHookNameInDev = 'useCallback';
       warnInvalidHookAccess();
@@ -2758,6 +2885,12 @@ if (__DEV__) {
       updateHookTypesDev();
       return updateEventListener(event);
     },
+    useOpaqueIdentifier(): OpaqueIDType | void {
+      currentHookNameInDev = 'useOpaqueIdentifier';
+      warnInvalidHookAccess();
+      updateHookTypesDev();
+      return updateOpaqueIdentifier();
+    },
   };
 
   InvalidNestedHooksDispatcherOnRerenderInDEV = {
@@ -2905,5 +3038,11 @@ if (__DEV__) {
       updateHookTypesDev();
       return updateEventListener(event);
     },
+    useOpaqueIdentifier(): OpaqueIDType | void {
+      currentHookNameInDev = 'useOpaqueIdentifier';
+      warnInvalidHookAccess();
+      updateHookTypesDev();
+      return rerenderOpaqueIdentifier();
+    },
   };
 }
diff --git a/packages/react-reconciler/src/ReactFiberHydrationContext.js b/packages/react-reconciler/src/ReactFiberHydrationContext.js
index 365bfb48dea3c..7f06c4d0ed60d 100644
--- a/packages/react-reconciler/src/ReactFiberHydrationContext.js
+++ b/packages/react-reconciler/src/ReactFiberHydrationContext.js
@@ -485,9 +485,14 @@ function resetHydrationState(): void {
   isHydrating = false;
 }
 
+function getIsHydrating(): boolean {
+  return isHydrating;
+}
+
 export {
   warnIfHydrating,
   enterHydrationState,
+  getIsHydrating,
   reenterHydrationStateFromDehydratedSuspenseInstance,
   resetHydrationState,
   tryToClaimNextHydratableInstance,
diff --git a/packages/react-reconciler/src/ReactFiberWorkLoop.js b/packages/react-reconciler/src/ReactFiberWorkLoop.js
index 5aab14db944bf..b82ed04cf75cb 100644
--- a/packages/react-reconciler/src/ReactFiberWorkLoop.js
+++ b/packages/react-reconciler/src/ReactFiberWorkLoop.js
@@ -145,7 +145,11 @@ import {
 } from './ReactFiberCommitWork';
 import {enqueueUpdate} from './ReactUpdateQueue';
 import {resetContextDependencies} from './ReactFiberNewContext';
-import {resetHooksAfterThrow, ContextOnlyDispatcher} from './ReactFiberHooks';
+import {
+  resetHooksAfterThrow,
+  ContextOnlyDispatcher,
+  getIsUpdatingOpaqueValueInRenderPhaseInDEV,
+} from './ReactFiberHooks';
 import {createCapturedValue} from './ReactCapturedValue';
 
 import {
@@ -2842,7 +2846,8 @@ function warnAboutRenderPhaseUpdatesInDEV(fiber) {
   if (__DEV__) {
     if (
       ReactCurrentDebugFiberIsRenderingInDEV &&
-      (executionContext & RenderContext) !== NoContext
+      (executionContext & RenderContext) !== NoContext &&
+      !getIsUpdatingOpaqueValueInRenderPhaseInDEV()
     ) {
       switch (fiber.tag) {
         case FunctionComponent:
diff --git a/packages/react-reconciler/src/forks/ReactFiberHostConfig.custom.js b/packages/react-reconciler/src/forks/ReactFiberHostConfig.custom.js
index dc45170134504..a9f6286e3bd8a 100644
--- a/packages/react-reconciler/src/forks/ReactFiberHostConfig.custom.js
+++ b/packages/react-reconciler/src/forks/ReactFiberHostConfig.custom.js
@@ -38,6 +38,7 @@ export opaque type ChildSet = mixed; // eslint-disable-line no-undef
 export opaque type TimeoutHandle = mixed; // eslint-disable-line no-undef
 export opaque type NoTimeout = mixed; // eslint-disable-line no-undef
 export opaque type RendererInspectionConfig = mixed; // eslint-disable-line no-undef
+export opaque type OpaqueIDType = mixed;
 export type EventResponder = any;
 export type ReactListenerEvent = Object;
 export type ReactListenerMap = Object;
@@ -82,6 +83,12 @@ export const mountEventListener = $$$hostConfig.mountEventListener;
 export const unmountEventListener = $$$hostConfig.unmountEventListener;
 export const validateEventListenerTarget =
   $$$hostConfig.validateEventListenerTarget;
+export const isOpaqueHydratingObject = $$$hostConfig.isOpaqueHydratingObject;
+export const makeOpaqueHydratingObject =
+  $$$hostConfig.makeOpaqueHydratingObject;
+export const makeClientId = $$$hostConfig.makeClientId;
+export const makeClientIdInDEV = $$$hostConfig.makeClientIdInDEV;
+export const makeServerId = $$$hostConfig.makeServerId;
 
 // -------------------
 //      Mutation
diff --git a/packages/react-test-renderer/src/ReactTestHostConfig.js b/packages/react-test-renderer/src/ReactTestHostConfig.js
index f4f66a3cd1c0d..c3eda48d2a4ea 100644
--- a/packages/react-test-renderer/src/ReactTestHostConfig.js
+++ b/packages/react-test-renderer/src/ReactTestHostConfig.js
@@ -14,6 +14,7 @@ import type {
 } from 'shared/ReactTypes';
 
 import {enableDeprecatedFlareAPI} from 'shared/ReactFeatureFlags';
+import {REACT_OPAQUE_ID_TYPE} from 'shared/ReactSymbols';
 
 export type Type = string;
 export type Props = Object;
@@ -44,6 +45,12 @@ export type ChildSet = void; // Unused
 export type TimeoutHandle = TimeoutID;
 export type NoTimeout = -1;
 export type EventResponder = any;
+export opaque type OpaqueIDType =
+  | string
+  | {
+      toString: () => string | void,
+      valueOf: () => string | void,
+    };
 
 export type ReactListenerEvent = Object;
 export type ReactListenerMap = Object;
@@ -381,6 +388,48 @@ export function beforeRemoveInstance(instance: any) {
   // noop
 }
 
+let clientId: number = 0;
+export function makeClientId(): OpaqueIDType {
+  return 'c_' + (clientId++).toString(36);
+}
+
+export function makeClientIdInDEV(warnOnAccessInDEV: () => void): OpaqueIDType {
+  const id = 'c_' + (clientId++).toString(36);
+  return {
+    toString() {
+      warnOnAccessInDEV();
+      return id;
+    },
+    valueOf() {
+      warnOnAccessInDEV();
+      return id;
+    },
+  };
+}
+
+let serverId: number = 0;
+export function makeServerId(): OpaqueIDType {
+  return 's_' + (serverId++).toString(36);
+}
+
+export function isOpaqueHydratingObject(value: mixed): boolean {
+  return (
+    value !== null &&
+    typeof value === 'object' &&
+    value.$$typeof === REACT_OPAQUE_ID_TYPE
+  );
+}
+
+export function makeOpaqueHydratingObject(
+  attemptToReadValue: () => void,
+): OpaqueIDType {
+  return {
+    $$typeof: REACT_OPAQUE_ID_TYPE,
+    toString: attemptToReadValue,
+    valueOf: attemptToReadValue,
+  };
+}
+
 export function registerEvent(event: any, rootContainerInstance: Container) {
   throw new Error('Not yet implemented.');
 }
diff --git a/packages/react/index.classic.fb.js b/packages/react/index.classic.fb.js
index ca2834be0fcac..998de2bec5caa 100644
--- a/packages/react/index.classic.fb.js
+++ b/packages/react/index.classic.fb.js
@@ -50,5 +50,6 @@ export {
   DEPRECATED_createResponder,
   // enableScopeAPI
   unstable_createScope,
+  unstable_useOpaqueIdentifier,
 } from './src/React';
 export {jsx, jsxs, jsxDEV} from './src/jsx/ReactJSX';
diff --git a/packages/react/index.experimental.js b/packages/react/index.experimental.js
index 79f1e235fe740..9c2a3d4d93553 100644
--- a/packages/react/index.experimental.js
+++ b/packages/react/index.experimental.js
@@ -45,4 +45,5 @@ export {
   unstable_withSuspenseConfig,
   // enableBlocksAPI
   block,
+  unstable_useOpaqueIdentifier,
 } from './src/React';
diff --git a/packages/react/index.js b/packages/react/index.js
index f97dd1fc0cd43..3ca22840f999e 100644
--- a/packages/react/index.js
+++ b/packages/react/index.js
@@ -76,4 +76,5 @@ export {
   DEPRECATED_createResponder,
   unstable_createFundamental,
   unstable_createScope,
+  unstable_useOpaqueIdentifier,
 } from './src/React';
diff --git a/packages/react/index.modern.fb.js b/packages/react/index.modern.fb.js
index c42da6dd343af..76a904d0c8cf0 100644
--- a/packages/react/index.modern.fb.js
+++ b/packages/react/index.modern.fb.js
@@ -49,5 +49,6 @@ export {
   DEPRECATED_createResponder,
   // enableScopeAPI
   unstable_createScope,
+  unstable_useOpaqueIdentifier,
 } from './src/React';
 export {jsx, jsxs, jsxDEV} from './src/jsx/ReactJSX';
diff --git a/packages/react/src/React.js b/packages/react/src/React.js
index 8484ef5886e96..d7896ad299722 100644
--- a/packages/react/src/React.js
+++ b/packages/react/src/React.js
@@ -45,6 +45,7 @@ import {
   useResponder,
   useTransition,
   useDeferredValue,
+  useOpaqueIdentifier,
 } from './ReactHooks';
 import {withSuspenseConfig} from './ReactBatchConfig';
 import {
@@ -117,4 +118,5 @@ export {
   createFundamental as unstable_createFundamental,
   // enableScopeAPI
   createScope as unstable_createScope,
+  useOpaqueIdentifier as unstable_useOpaqueIdentifier,
 };
diff --git a/packages/react/src/ReactHooks.js b/packages/react/src/ReactHooks.js
index 38a6a363481b2..acc47e1d6b9f8 100644
--- a/packages/react/src/ReactHooks.js
+++ b/packages/react/src/ReactHooks.js
@@ -15,6 +15,8 @@ import type {
   ReactEventResponder,
   ReactEventResponderListener,
 } from 'shared/ReactTypes';
+import type {OpaqueIDType} from 'react-reconciler/src/ReactFiberHostConfig';
+
 import invariant from 'shared/invariant';
 import {REACT_RESPONDER_TYPE} from 'shared/ReactSymbols';
 
@@ -181,6 +183,11 @@ export function useDeferredValue<T>(value: T, config: ?Object): T {
   return dispatcher.useDeferredValue(value, config);
 }
 
+export function useOpaqueIdentifier(): OpaqueIDType | void {
+  const dispatcher = resolveDispatcher();
+  return dispatcher.useOpaqueIdentifier();
+}
+
 export function useMutableSource<Source, Snapshot>(
   source: MutableSource<Source>,
   getSnapshot: MutableSourceGetSnapshotFn<Source, Snapshot>,
diff --git a/packages/shared/ReactSymbols.js b/packages/shared/ReactSymbols.js
index 77979459e9626..53c994cf3bfeb 100644
--- a/packages/shared/ReactSymbols.js
+++ b/packages/shared/ReactSymbols.js
@@ -26,6 +26,7 @@ export let REACT_SERVER_BLOCK_TYPE = 0xeada;
 export let REACT_FUNDAMENTAL_TYPE = 0xead5;
 export let REACT_RESPONDER_TYPE = 0xead6;
 export let REACT_SCOPE_TYPE = 0xead7;
+export let REACT_OPAQUE_ID_TYPE = 0xeae0;
 
 if (typeof Symbol === 'function' && Symbol.for) {
   const symbolFor = Symbol.for;
@@ -46,6 +47,7 @@ if (typeof Symbol === 'function' && Symbol.for) {
   REACT_FUNDAMENTAL_TYPE = symbolFor('react.fundamental');
   REACT_RESPONDER_TYPE = symbolFor('react.responder');
   REACT_SCOPE_TYPE = symbolFor('react.scope');
+  REACT_OPAQUE_ID_TYPE = symbolFor('react.opaque.id');
 }
 
 const MAYBE_ITERATOR_SYMBOL = typeof Symbol === 'function' && Symbol.iterator;
diff --git a/scripts/error-codes/codes.json b/scripts/error-codes/codes.json
index e8f9108d92fcc..49d179af10be2 100644
--- a/scripts/error-codes/codes.json
+++ b/scripts/error-codes/codes.json
@@ -351,5 +351,6 @@
   "351": "Unsupported type.",
   "352": "React Blocks (and Lazy Components) are expected to be replaced by a compiler on the server. Try configuring your compiler set up and avoid using React.lazy inside of Blocks.",
   "353": "A server block should never encode any other slots. This is a bug in React.",
-  "354": "getInspectorDataForViewAtPoint() is not available in production."
+  "354": "getInspectorDataForViewAtPoint() is not available in production.",
+  "355": "The object passed back from useOpaqueIdentifier is meant to be passed through to attributes only. Do not read the value directly."
 }