diff --git a/unirest-bdd-tests/src/test/java/BehaviorTests/MultiPartFormPostingTest.java b/unirest-bdd-tests/src/test/java/BehaviorTests/MultiPartFormPostingTest.java
index c974d356..3fb0539f 100644
--- a/unirest-bdd-tests/src/test/java/BehaviorTests/MultiPartFormPostingTest.java
+++ b/unirest-bdd-tests/src/test/java/BehaviorTests/MultiPartFormPostingTest.java
@@ -476,4 +476,20 @@ void defaultMediaTypes() {
                 });
 
     }
+
+    @Test
+    void settingTheBoundary() {
+        String boundary = "ABC-123-BOUNDARY";
+
+        Unirest.post(MockServer.POST)
+                .field("spidey", rezFile("/spidey.pdf"))
+                .field("something", "else")
+                .boundary(boundary)
+                .asObject(RequestCapture.class)
+                .getBody()
+                .assertHeader("Content-Type", h -> {
+                   h.assertParam("boundary", boundary);
+                });
+
+    }
 }
diff --git a/unirest/src/main/java/kong/unirest/core/Body.java b/unirest/src/main/java/kong/unirest/core/Body.java
index bb8e744c..0e61c613 100644
--- a/unirest/src/main/java/kong/unirest/core/Body.java
+++ b/unirest/src/main/java/kong/unirest/core/Body.java
@@ -56,6 +56,10 @@ default ProgressMonitor getMonitor(){
         return null;
     }
 
+    default String getBoundary() {
+        return null;
+    }
+
     default BodyPart getField(String name){
         return multiParts()
                 .stream()
diff --git a/unirest/src/main/java/kong/unirest/core/HttpRequestMultiPart.java b/unirest/src/main/java/kong/unirest/core/HttpRequestMultiPart.java
index 06d36df1..bb70f2f7 100644
--- a/unirest/src/main/java/kong/unirest/core/HttpRequestMultiPart.java
+++ b/unirest/src/main/java/kong/unirest/core/HttpRequestMultiPart.java
@@ -37,6 +37,7 @@ class HttpRequestMultiPart extends BaseRequest<MultipartBody> implements Multipa
     private Charset charSet;
     private boolean forceMulti = false;
     private ProgressMonitor monitor;
+    private String boundary;
 
     HttpRequestMultiPart(HttpRequestBody httpRequest) {
         super(httpRequest);
@@ -136,6 +137,20 @@ public MultipartBody uploadMonitor(ProgressMonitor uploadMonitor) {
         return this;
     }
 
+    @Override
+    public MultipartBody boundary(String boundaryIdentifier) {
+        this.boundary = boundaryIdentifier;
+        return this;
+    }
+
+    @Override
+    public String getBoundary() {
+        if(boundary == null){
+            boundary = UUID.randomUUID().toString();
+        }
+        return boundary;
+    }
+
     @Override
     public Charset getCharset() {
         return this.charSet;
diff --git a/unirest/src/main/java/kong/unirest/core/MultipartBody.java b/unirest/src/main/java/kong/unirest/core/MultipartBody.java
index e09ca2e2..49387b8d 100644
--- a/unirest/src/main/java/kong/unirest/core/MultipartBody.java
+++ b/unirest/src/main/java/kong/unirest/core/MultipartBody.java
@@ -160,4 +160,12 @@ public interface MultipartBody extends HttpRequest<MultipartBody>, Body {
      * @return The same MultipartBody
      * */
     MultipartBody uploadMonitor(ProgressMonitor monitor);
+
+    /**
+     * Sets the value to use as the boundary identifier.
+     * see https://datatracker.ietf.org/doc/html/rfc2046
+     * @param boundaryIdentifier the value
+     * @return The same MultipartBody
+     */
+    MultipartBody boundary(String boundaryIdentifier);
 }
diff --git a/unirest/src/main/java/kong/unirest/core/java/BodyBuilder.java b/unirest/src/main/java/kong/unirest/core/java/BodyBuilder.java
index 6965e517..04ae96d2 100644
--- a/unirest/src/main/java/kong/unirest/core/java/BodyBuilder.java
+++ b/unirest/src/main/java/kong/unirest/core/java/BodyBuilder.java
@@ -74,7 +74,7 @@ private java.net.http.HttpRequest.BodyPublisher mapToMultipart(Body o) {
                 );
             }
 
-            MultipartBodyPublisher.Builder builder = MultipartBodyPublisher.newBuilder();
+            var builder = MultipartBodyPublisher.newBuilder(o.getBoundary());
             o.multiParts().forEach(part -> {
                 setMultiPart(o, builder, part);
             });
diff --git a/unirest/src/main/java/kong/unirest/core/java/MultipartBodyPublisher.java b/unirest/src/main/java/kong/unirest/core/java/MultipartBodyPublisher.java
index 9f9b5412..8778f4f6 100644
--- a/unirest/src/main/java/kong/unirest/core/java/MultipartBodyPublisher.java
+++ b/unirest/src/main/java/kong/unirest/core/java/MultipartBodyPublisher.java
@@ -38,7 +38,6 @@
 import java.nio.file.Path;
 import java.util.ArrayList;
 import java.util.List;
-import java.util.UUID;
 import java.util.concurrent.Flow.Subscriber;
 
 import static java.nio.charset.StandardCharsets.UTF_8;
@@ -56,12 +55,13 @@ final class MultipartBodyPublisher implements BodyPublisher {
 
     private final List<Part> parts;
     private final ProgressMonitor monitor;
-    private final String boundary = UUID.randomUUID().toString();
+    private final String boundary;
     private long contentLength;
 
-    private MultipartBodyPublisher(List<Part> parts, ProgressMonitor monitor) {
+    private MultipartBodyPublisher(List<Part> parts, ProgressMonitor monitor, String boundary) {
         this.parts = parts;
         this.monitor = monitor;
+        this.boundary = boundary;
         contentLength = UNINITIALIZED_LENGTH;
     }
 
@@ -119,15 +119,17 @@ private static void appendHeader(StringBuilder target, String name, String value
     }
 
     /** Returns a new {@code MultipartBodyPublisher.Builder}. */
-    static MultipartBodyPublisher.Builder newBuilder() {
-        return new MultipartBodyPublisher.Builder();
+    static MultipartBodyPublisher.Builder newBuilder(String boundary) {
+        return new MultipartBodyPublisher.Builder(boundary);
     }
 
     static final class Builder {
 
         private final List<Part> parts;
+        private final String boundary;
 
-        Builder() {
+        Builder(String boundary) {
+            this.boundary = boundary;
             parts = new ArrayList<>();
         }
 
@@ -220,7 +222,7 @@ MultipartBodyPublisher build(ProgressMonitor monitor) {
             if (!!addedParts.isEmpty()) {
                 throw new UnirestException("at least one part should be added");
             }
-            return new MultipartBodyPublisher(addedParts, monitor);
+            return new MultipartBodyPublisher(addedParts, monitor, boundary);
         }
     }
 }
\ No newline at end of file