diff --git a/js/public/GCAPI.h b/js/public/GCAPI.h
index 98901cf9b143..ace9eab4263f 100644
--- a/js/public/GCAPI.h
+++ b/js/public/GCAPI.h
@@ -396,6 +396,16 @@ typedef void (*JSWeakPointerCompartmentCallback)(JSContext* cx,
                                                  JS::Compartment* comp,
                                                  void* data);
 
+/*
+ * This is called to tell the embedding that the FinalizationGroup object
+ * |group| has cleanup work, and that then engine should be called back at an
+ * appropriate later time to perform this cleanup.
+ *
+ * This callback must not do anything that could cause GC.
+ */
+using JSHostCleanupFinalizationGroupCallback = void (*)(JSObject* group,
+                                                        void* data);
+
 /**
  * Each external string has a pointer to JSExternalStringCallbacks. Embedders
  * can use this to implement custom finalization or memory reporting behavior.
@@ -1087,6 +1097,9 @@ extern JS_PUBLIC_API bool IsIdleGCTaskNeeded(JSRuntime* rt);
 
 extern JS_PUBLIC_API void RunIdleTimeGCTask(JSRuntime* rt);
 
+extern JS_PUBLIC_API void SetHostCleanupFinalizationGroupCallback(
+    JSContext* cx, JSHostCleanupFinalizationGroupCallback cb, void* data);
+
 }  // namespace JS
 
 namespace js {
diff --git a/js/src/gc/GC.cpp b/js/src/gc/GC.cpp
index ce4a2eb521f4..7d1fcd014858 100644
--- a/js/src/gc/GC.cpp
+++ b/js/src/gc/GC.cpp
@@ -213,6 +213,7 @@
 #include "jstypes.h"
 #include "jsutil.h"
 
+#include "builtin/FinalizationGroupObject.h"
 #include "debugger/DebugAPI.h"
 #include "gc/FindSCCs.h"
 #include "gc/FreeOp.h"
@@ -1546,6 +1547,20 @@ void GCRuntime::callFinalizeCallbacks(JSFreeOp* fop,
   }
 }
 
+void GCRuntime::setHostCleanupFinalizationGroupCallback(
+    JSHostCleanupFinalizationGroupCallback callback, void* data) {
+  hostCleanupFinalizationGroupCallback = {callback, data};
+}
+
+void GCRuntime::callHostCleanupFinalizationGroupCallback(
+    FinalizationGroupObject* group) {
+  JS::AutoSuppressGCAnalysis nogc;
+  auto& callback = hostCleanupFinalizationGroupCallback;
+  if (callback.op) {
+    callback.op(group, callback.data);
+  }
+}
+
 bool GCRuntime::addWeakPointerZonesCallback(JSWeakPointerZonesCallback callback,
                                             void* data) {
   return updateWeakPointerZonesCallbacks.ref().append(
diff --git a/js/src/gc/GCRuntime.h b/js/src/gc/GCRuntime.h
index 8886506f00f6..3b9bcb3cd3ad 100644
--- a/js/src/gc/GCRuntime.h
+++ b/js/src/gc/GCRuntime.h
@@ -30,6 +30,7 @@ class AutoAccessAtomsZone;
 class AutoLockGC;
 class AutoLockGCBgAlloc;
 class AutoLockHelperThreadState;
+class FinalizationGroupObject;
 class VerifyPreTracer;
 class ZoneAllocator;
 
@@ -395,6 +396,9 @@ class GCRuntime {
   MOZ_MUST_USE bool addFinalizeCallback(JSFinalizeCallback callback,
                                         void* data);
   void removeFinalizeCallback(JSFinalizeCallback func);
+  void setHostCleanupFinalizationGroupCallback(
+      JSHostCleanupFinalizationGroupCallback callback, void* data);
+  void callHostCleanupFinalizationGroupCallback(FinalizationGroupObject* group);
   MOZ_MUST_USE bool addWeakPointerZonesCallback(
       JSWeakPointerZonesCallback callback, void* data);
   void removeWeakPointerZonesCallback(JSWeakPointerZonesCallback callback);
@@ -1045,6 +1049,8 @@ class GCRuntime {
   Callback<JS::DoCycleCollectionCallback> gcDoCycleCollectionCallback;
   Callback<JSObjectsTenuredCallback> tenuredCallback;
   CallbackVector<JSFinalizeCallback> finalizeCallbacks;
+  Callback<JSHostCleanupFinalizationGroupCallback>
+      hostCleanupFinalizationGroupCallback;
   CallbackVector<JSWeakPointerZonesCallback> updateWeakPointerZonesCallbacks;
   CallbackVector<JSWeakPointerCompartmentCallback>
       updateWeakPointerCompartmentCallbacks;
diff --git a/js/src/jsapi.cpp b/js/src/jsapi.cpp
index 8a48eab5bad7..59daed2ce962 100644
--- a/js/src/jsapi.cpp
+++ b/js/src/jsapi.cpp
@@ -1285,6 +1285,12 @@ JS_PUBLIC_API void JS_RemoveFinalizeCallback(JSContext* cx,
   cx->runtime()->gc.removeFinalizeCallback(cb);
 }
 
+JS_PUBLIC_API void JS::SetHostCleanupFinalizationGroupCallback(
+    JSContext* cx, JSHostCleanupFinalizationGroupCallback cb, void* data) {
+  AssertHeapIsIdle();
+  cx->runtime()->gc.setHostCleanupFinalizationGroupCallback(cb, data);
+}
+
 JS_PUBLIC_API bool JS_AddWeakPointerZonesCallback(JSContext* cx,
                                                   JSWeakPointerZonesCallback cb,
                                                   void* data) {