diff --git a/apps/parsley/src/gql/generated/types.ts b/apps/parsley/src/gql/generated/types.ts
index 24e9b8eb8..22f56ae77 100644
--- a/apps/parsley/src/gql/generated/types.ts
+++ b/apps/parsley/src/gql/generated/types.ts
@@ -1696,6 +1696,7 @@ export type Project = {
   isFavorite: Scalars["Boolean"]["output"];
   manualPrTestingEnabled?: Maybe<Scalars["Boolean"]["output"]>;
   notifyOnBuildFailure?: Maybe<Scalars["Boolean"]["output"]>;
+  oldestAllowedMergeBase: Scalars["String"]["output"];
   owner: Scalars["String"]["output"];
   parsleyFilters?: Maybe<Array<ParsleyFilter>>;
   patchTriggerAliases?: Maybe<Array<PatchTriggerAlias>>;
@@ -1832,6 +1833,7 @@ export type ProjectInput = {
   identifier?: InputMaybe<Scalars["String"]["input"]>;
   manualPrTestingEnabled?: InputMaybe<Scalars["Boolean"]["input"]>;
   notifyOnBuildFailure?: InputMaybe<Scalars["Boolean"]["input"]>;
+  oldestAllowedMergeBase?: InputMaybe<Scalars["String"]["input"]>;
   owner?: InputMaybe<Scalars["String"]["input"]>;
   parsleyFilters?: InputMaybe<Array<ParsleyFilterInput>>;
   patchTriggerAliases?: InputMaybe<Array<PatchTriggerAliasInput>>;
@@ -2168,6 +2170,7 @@ export type RepoRef = {
   id: Scalars["String"]["output"];
   manualPrTestingEnabled: Scalars["Boolean"]["output"];
   notifyOnBuildFailure: Scalars["Boolean"]["output"];
+  oldestAllowedMergeBase: Scalars["String"]["output"];
   owner: Scalars["String"]["output"];
   parsleyFilters?: Maybe<Array<ParsleyFilter>>;
   patchTriggerAliases?: Maybe<Array<PatchTriggerAlias>>;
@@ -2211,6 +2214,7 @@ export type RepoRefInput = {
   id: Scalars["String"]["input"];
   manualPrTestingEnabled?: InputMaybe<Scalars["Boolean"]["input"]>;
   notifyOnBuildFailure?: InputMaybe<Scalars["Boolean"]["input"]>;
+  oldestAllowedMergeBase?: InputMaybe<Scalars["String"]["input"]>;
   owner?: InputMaybe<Scalars["String"]["input"]>;
   parsleyFilters?: InputMaybe<Array<ParsleyFilterInput>>;
   patchTriggerAliases?: InputMaybe<Array<PatchTriggerAliasInput>>;
diff --git a/apps/spruce/src/gql/fragments/projectSettings/githubCommitQueue.graphql b/apps/spruce/src/gql/fragments/projectSettings/githubCommitQueue.graphql
index bd29f8813..2409f0627 100644
--- a/apps/spruce/src/gql/fragments/projectSettings/githubCommitQueue.graphql
+++ b/apps/spruce/src/gql/fragments/projectSettings/githubCommitQueue.graphql
@@ -11,6 +11,7 @@ fragment ProjectGithubSettings on Project {
   gitTagAuthorizedUsers
   gitTagVersionsEnabled
   manualPrTestingEnabled
+  oldestAllowedMergeBase
   prTestingEnabled
 }
 
@@ -27,6 +28,7 @@ fragment RepoGithubSettings on RepoRef {
   gitTagAuthorizedUsers
   gitTagVersionsEnabled
   manualPrTestingEnabled
+  oldestAllowedMergeBase
   prTestingEnabled
 }
 
diff --git a/apps/spruce/src/gql/generated/types.ts b/apps/spruce/src/gql/generated/types.ts
index 1d4f15717..c32300857 100644
--- a/apps/spruce/src/gql/generated/types.ts
+++ b/apps/spruce/src/gql/generated/types.ts
@@ -1696,6 +1696,7 @@ export type Project = {
   isFavorite: Scalars["Boolean"]["output"];
   manualPrTestingEnabled?: Maybe<Scalars["Boolean"]["output"]>;
   notifyOnBuildFailure?: Maybe<Scalars["Boolean"]["output"]>;
+  oldestAllowedMergeBase: Scalars["String"]["output"];
   owner: Scalars["String"]["output"];
   parsleyFilters?: Maybe<Array<ParsleyFilter>>;
   patchTriggerAliases?: Maybe<Array<PatchTriggerAlias>>;
@@ -1832,6 +1833,7 @@ export type ProjectInput = {
   identifier?: InputMaybe<Scalars["String"]["input"]>;
   manualPrTestingEnabled?: InputMaybe<Scalars["Boolean"]["input"]>;
   notifyOnBuildFailure?: InputMaybe<Scalars["Boolean"]["input"]>;
+  oldestAllowedMergeBase?: InputMaybe<Scalars["String"]["input"]>;
   owner?: InputMaybe<Scalars["String"]["input"]>;
   parsleyFilters?: InputMaybe<Array<ParsleyFilterInput>>;
   patchTriggerAliases?: InputMaybe<Array<PatchTriggerAliasInput>>;
@@ -2168,6 +2170,7 @@ export type RepoRef = {
   id: Scalars["String"]["output"];
   manualPrTestingEnabled: Scalars["Boolean"]["output"];
   notifyOnBuildFailure: Scalars["Boolean"]["output"];
+  oldestAllowedMergeBase: Scalars["String"]["output"];
   owner: Scalars["String"]["output"];
   parsleyFilters?: Maybe<Array<ParsleyFilter>>;
   patchTriggerAliases?: Maybe<Array<PatchTriggerAlias>>;
@@ -2211,6 +2214,7 @@ export type RepoRefInput = {
   id: Scalars["String"]["input"];
   manualPrTestingEnabled?: InputMaybe<Scalars["Boolean"]["input"]>;
   notifyOnBuildFailure?: InputMaybe<Scalars["Boolean"]["input"]>;
+  oldestAllowedMergeBase?: InputMaybe<Scalars["String"]["input"]>;
   owner?: InputMaybe<Scalars["String"]["input"]>;
   parsleyFilters?: InputMaybe<Array<ParsleyFilterInput>>;
   patchTriggerAliases?: InputMaybe<Array<PatchTriggerAliasInput>>;
@@ -3585,6 +3589,7 @@ export type ProjectGithubSettingsFragment = {
   gitTagAuthorizedUsers?: Array<string> | null;
   gitTagVersionsEnabled?: boolean | null;
   manualPrTestingEnabled?: boolean | null;
+  oldestAllowedMergeBase: string;
   prTestingEnabled?: boolean | null;
   commitQueue: {
     __typename?: "CommitQueueParams";
@@ -3603,6 +3608,7 @@ export type RepoGithubSettingsFragment = {
   gitTagAuthorizedUsers?: Array<string> | null;
   gitTagVersionsEnabled: boolean;
   manualPrTestingEnabled: boolean;
+  oldestAllowedMergeBase: string;
   prTestingEnabled: boolean;
   commitQueue: {
     __typename?: "RepoCommitQueueParams";
@@ -3624,6 +3630,7 @@ export type ProjectGithubCommitQueueFragment = {
     gitTagAuthorizedUsers?: Array<string> | null;
     gitTagVersionsEnabled?: boolean | null;
     manualPrTestingEnabled?: boolean | null;
+    oldestAllowedMergeBase: string;
     prTestingEnabled?: boolean | null;
     commitQueue: {
       __typename?: "CommitQueueParams";
@@ -3646,6 +3653,7 @@ export type RepoGithubCommitQueueFragment = {
     gitTagAuthorizedUsers?: Array<string> | null;
     gitTagVersionsEnabled: boolean;
     manualPrTestingEnabled: boolean;
+    oldestAllowedMergeBase: string;
     prTestingEnabled: boolean;
     commitQueue: {
       __typename?: "RepoCommitQueueParams";
@@ -3668,6 +3676,7 @@ export type ProjectEventGithubCommitQueueFragment = {
     gitTagAuthorizedUsers?: Array<string> | null;
     gitTagVersionsEnabled?: boolean | null;
     manualPrTestingEnabled?: boolean | null;
+    oldestAllowedMergeBase: string;
     prTestingEnabled?: boolean | null;
     commitQueue: {
       __typename?: "CommitQueueParams";
@@ -3727,6 +3736,7 @@ export type ProjectSettingsFieldsFragment = {
     gitTagAuthorizedUsers?: Array<string> | null;
     gitTagVersionsEnabled?: boolean | null;
     manualPrTestingEnabled?: boolean | null;
+    oldestAllowedMergeBase: string;
     prTestingEnabled?: boolean | null;
     containerSizeDefinitions?: Array<{
       __typename?: "ContainerResources";
@@ -3933,6 +3943,7 @@ export type RepoSettingsFieldsFragment = {
     gitTagAuthorizedUsers?: Array<string> | null;
     gitTagVersionsEnabled: boolean;
     manualPrTestingEnabled: boolean;
+    oldestAllowedMergeBase: string;
     prTestingEnabled: boolean;
     containerSizeDefinitions?: Array<{
       __typename?: "ContainerResources";
@@ -4335,6 +4346,7 @@ export type ProjectEventSettingsFragment = {
     gitTagAuthorizedUsers?: Array<string> | null;
     gitTagVersionsEnabled?: boolean | null;
     manualPrTestingEnabled?: boolean | null;
+    oldestAllowedMergeBase: string;
     prTestingEnabled?: boolean | null;
     taskSync: {
       __typename?: "TaskSyncOptions";
@@ -6806,6 +6818,7 @@ export type ProjectEventLogsQuery = {
           gitTagAuthorizedUsers?: Array<string> | null;
           gitTagVersionsEnabled?: boolean | null;
           manualPrTestingEnabled?: boolean | null;
+          oldestAllowedMergeBase: string;
           prTestingEnabled?: boolean | null;
           taskSync: {
             __typename?: "TaskSyncOptions";
@@ -7019,6 +7032,7 @@ export type ProjectEventLogsQuery = {
           gitTagAuthorizedUsers?: Array<string> | null;
           gitTagVersionsEnabled?: boolean | null;
           manualPrTestingEnabled?: boolean | null;
+          oldestAllowedMergeBase: string;
           prTestingEnabled?: boolean | null;
           taskSync: {
             __typename?: "TaskSyncOptions";
@@ -7305,6 +7319,7 @@ export type ProjectSettingsQuery = {
       gitTagAuthorizedUsers?: Array<string> | null;
       gitTagVersionsEnabled?: boolean | null;
       manualPrTestingEnabled?: boolean | null;
+      oldestAllowedMergeBase: string;
       prTestingEnabled?: boolean | null;
       containerSizeDefinitions?: Array<{
         __typename?: "ContainerResources";
@@ -7572,6 +7587,7 @@ export type RepoEventLogsQuery = {
           gitTagAuthorizedUsers?: Array<string> | null;
           gitTagVersionsEnabled?: boolean | null;
           manualPrTestingEnabled?: boolean | null;
+          oldestAllowedMergeBase: string;
           prTestingEnabled?: boolean | null;
           taskSync: {
             __typename?: "TaskSyncOptions";
@@ -7785,6 +7801,7 @@ export type RepoEventLogsQuery = {
           gitTagAuthorizedUsers?: Array<string> | null;
           gitTagVersionsEnabled?: boolean | null;
           manualPrTestingEnabled?: boolean | null;
+          oldestAllowedMergeBase: string;
           prTestingEnabled?: boolean | null;
           taskSync: {
             __typename?: "TaskSyncOptions";
@@ -8002,6 +8019,7 @@ export type RepoSettingsQuery = {
       gitTagAuthorizedUsers?: Array<string> | null;
       gitTagVersionsEnabled: boolean;
       manualPrTestingEnabled: boolean;
+      oldestAllowedMergeBase: string;
       prTestingEnabled: boolean;
       containerSizeDefinitions?: Array<{
         __typename?: "ContainerResources";
diff --git a/apps/spruce/src/pages/projectSettings/CopyProjectModal.test.tsx b/apps/spruce/src/pages/projectSettings/CopyProjectModal.test.tsx
index 431a2038c..2b111109a 100644
--- a/apps/spruce/src/pages/projectSettings/CopyProjectModal.test.tsx
+++ b/apps/spruce/src/pages/projectSettings/CopyProjectModal.test.tsx
@@ -300,6 +300,7 @@ const projectSettingsMock: ApolloMock<
           batchTime: 60,
           remotePath: ".arst.yml",
           spawnHostScriptPath: "",
+          oldestAllowedMergeBase: "",
           dispatchingDisabled: false,
           versionControlEnabled: false,
           deactivatePrevious: true,
diff --git a/apps/spruce/src/pages/projectSettings/tabs/EventLogTab/EventLogTab.test.tsx b/apps/spruce/src/pages/projectSettings/tabs/EventLogTab/EventLogTab.test.tsx
index b28061c8c..b06d166b5 100644
--- a/apps/spruce/src/pages/projectSettings/tabs/EventLogTab/EventLogTab.test.tsx
+++ b/apps/spruce/src/pages/projectSettings/tabs/EventLogTab/EventLogTab.test.tsx
@@ -94,6 +94,7 @@ const projectEventsQuery: ProjectEventLogsQuery = {
             displayName: "Spruce",
             batchTime: 60,
             remotePath: ".evergreen.yml",
+            oldestAllowedMergeBase: "",
             spawnHostScriptPath: "",
             dispatchingDisabled: false,
             versionControlEnabled: false,
@@ -182,6 +183,7 @@ const projectEventsQuery: ProjectEventLogsQuery = {
             batchTime: 30,
             remotePath: ".srat.yml",
             spawnHostScriptPath: "",
+            oldestAllowedMergeBase: "",
             dispatchingDisabled: false,
             versionControlEnabled: false,
             deactivatePrevious: true,
diff --git a/apps/spruce/src/pages/projectSettings/tabs/GithubCommitQueueTab/getFormSchema.tsx b/apps/spruce/src/pages/projectSettings/tabs/GithubCommitQueueTab/getFormSchema.tsx
index 339c68ebd..ae97604d6 100644
--- a/apps/spruce/src/pages/projectSettings/tabs/GithubCommitQueueTab/getFormSchema.tsx
+++ b/apps/spruce/src/pages/projectSettings/tabs/GithubCommitQueueTab/getFormSchema.tsx
@@ -85,6 +85,10 @@ export const getFormSchema = (
                 repoData?.github?.manualPrTestingEnabled,
               ),
             },
+            oldestAllowedMergeBase: {
+              type: "string" as "string",
+              title: "Oldest Allowed Merge Base",
+            },
             prTesting: {
               type: "object" as "object",
               title: "GitHub Patch Definitions",
@@ -342,6 +346,22 @@ export const getFormSchema = (
             "PR Testing",
           ),
         },
+        oldestAllowedMergeBase: {
+          "ui:description":
+            "Specify the oldest commit SHA on your project branch that is allowed to be a merge base for a PR",
+          "ui:optional": true,
+          ...placeholderIf(repoData?.github?.oldestAllowedMergeBase),
+          ...hideIf(
+            fieldDisabled(
+              formData?.github?.prTestingEnabled,
+              repoData?.github?.prTestingEnabled,
+            ) &&
+              fieldDisabled(
+                formData?.github?.manualPrTestingEnabled,
+                repoData?.github?.manualPrTestingEnabled,
+              ),
+          ),
+        },
         prTesting: {
           ...hideIf(
             fieldDisabled(
diff --git a/apps/spruce/src/pages/projectSettings/tabs/GithubCommitQueueTab/transformers.test.ts b/apps/spruce/src/pages/projectSettings/tabs/GithubCommitQueueTab/transformers.test.ts
index 7f2378cd2..c4fc5f30c 100644
--- a/apps/spruce/src/pages/projectSettings/tabs/GithubCommitQueueTab/transformers.test.ts
+++ b/apps/spruce/src/pages/projectSettings/tabs/GithubCommitQueueTab/transformers.test.ts
@@ -45,6 +45,7 @@ const projectForm: GCQFormState = {
   github: {
     prTestingEnabled: null,
     manualPrTestingEnabled: null,
+    oldestAllowedMergeBase: "abc",
     prTesting: {
       githubPrAliasesOverride: true,
       githubPrAliases: [
@@ -150,6 +151,7 @@ const projectResult: Pick<
     id: "project",
     prTestingEnabled: null,
     manualPrTestingEnabled: null,
+    oldestAllowedMergeBase: "abc",
     githubChecksEnabled: null,
     gitTagVersionsEnabled: null,
     gitTagAuthorizedUsers: ["privileged"],
@@ -205,6 +207,7 @@ const repoForm: GCQFormState = {
   github: {
     prTestingEnabled: false,
     manualPrTestingEnabled: false,
+    oldestAllowedMergeBase: "abc",
     prTesting: {
       githubPrAliasesOverride: true,
       githubPrAliases: [],
@@ -292,6 +295,7 @@ const repoResult: Pick<RepoSettingsInput, "repoId" | "projectRef" | "aliases"> =
       gitTagVersionsEnabled: false,
       gitTagAuthorizedUsers: ["admin"],
       gitTagAuthorizedTeams: [],
+      oldestAllowedMergeBase: "abc",
       commitQueue: {
         enabled: true,
         message: "Commit Queue Message",
@@ -319,6 +323,7 @@ const mergedForm: GCQFormState = {
   github: {
     prTestingEnabled: null,
     manualPrTestingEnabled: null,
+    oldestAllowedMergeBase: "abc",
     prTesting: {
       githubPrAliasesOverride: true,
       githubPrAliases: [
diff --git a/apps/spruce/src/pages/projectSettings/tabs/GithubCommitQueueTab/transformers.ts b/apps/spruce/src/pages/projectSettings/tabs/GithubCommitQueueTab/transformers.ts
index 2d23f813c..6ecaf46ce 100644
--- a/apps/spruce/src/pages/projectSettings/tabs/GithubCommitQueueTab/transformers.ts
+++ b/apps/spruce/src/pages/projectSettings/tabs/GithubCommitQueueTab/transformers.ts
@@ -40,6 +40,7 @@ export const gqlToForm = ((data, options) => {
     gitTagVersionsEnabled,
     githubChecksEnabled,
     manualPrTestingEnabled,
+    oldestAllowedMergeBase,
     prTestingEnabled,
   } = projectRef;
 
@@ -75,6 +76,7 @@ export const gqlToForm = ((data, options) => {
         githubCheckAliases,
       },
       gitTagVersionsEnabled,
+      oldestAllowedMergeBase,
       users: {
         gitTagAuthorizedUsersOverride:
           projectType !== ProjectType.AttachedProject ||
@@ -121,6 +123,7 @@ export const formToGql = ((
       githubChecks,
       githubChecksEnabled,
       manualPrTestingEnabled,
+      oldestAllowedMergeBase,
       prTesting,
       prTestingEnabled,
       teams: { gitTagAuthorizedTeams, gitTagAuthorizedTeamsOverride },
@@ -136,6 +139,7 @@ export const formToGql = ((
     manualPrTestingEnabled,
     githubChecksEnabled,
     gitTagVersionsEnabled,
+    oldestAllowedMergeBase,
     gitTagAuthorizedUsers: gitTagAuthorizedUsersOverride
       ? gitTagAuthorizedUsers
       : null,
diff --git a/apps/spruce/src/pages/projectSettings/tabs/GithubCommitQueueTab/types.ts b/apps/spruce/src/pages/projectSettings/tabs/GithubCommitQueueTab/types.ts
index e64311469..102599b26 100644
--- a/apps/spruce/src/pages/projectSettings/tabs/GithubCommitQueueTab/types.ts
+++ b/apps/spruce/src/pages/projectSettings/tabs/GithubCommitQueueTab/types.ts
@@ -16,6 +16,7 @@ export interface GCQFormState {
         githubPrAliases: Array<AliasFormType>;
       };
     };
+    oldestAllowedMergeBase: string;
     githubTriggerAliases: ProjectPatchAliasSettingsFragment["patchTriggerAliases"];
     githubChecksEnabled: boolean;
     githubChecks: {
diff --git a/apps/spruce/src/pages/projectSettings/tabs/testData.ts b/apps/spruce/src/pages/projectSettings/tabs/testData.ts
index 386f221cb..f439d09e8 100644
--- a/apps/spruce/src/pages/projectSettings/tabs/testData.ts
+++ b/apps/spruce/src/pages/projectSettings/tabs/testData.ts
@@ -44,6 +44,7 @@ const projectBase: ProjectSettingsQuery["projectSettings"] = {
     notifyOnBuildFailure: null,
     batchTime: 0,
     remotePath: null,
+    oldestAllowedMergeBase: "abc",
     spawnHostScriptPath: null,
     dispatchingDisabled: null,
     versionControlEnabled: true,
@@ -178,6 +179,7 @@ const repoBase: RepoSettingsQuery["repoSettings"] = {
     batchTime: 12,
     remotePath: "evergreen.yml",
     spawnHostScriptPath: "/test/path",
+    oldestAllowedMergeBase: "abc",
     dispatchingDisabled: true,
     versionControlEnabled: false,
     deactivatePrevious: true,