diff --git a/dom/base/nsGlobalWindow.cpp b/dom/base/nsGlobalWindow.cpp
index c676e5f1f309..3ed57bdf8219 100644
--- a/dom/base/nsGlobalWindow.cpp
+++ b/dom/base/nsGlobalWindow.cpp
@@ -187,6 +187,7 @@
 #include "mozilla/dom/MessagePort.h"
 #include "mozilla/dom/MessagePortBinding.h"
 #include "mozilla/dom/indexedDB/IDBFactory.h"
+#include "mozilla/dom/Promise.h"
 
 #include "mozilla/dom/StructuredCloneTags.h"
 
@@ -6370,6 +6371,14 @@ nsGlobalWindow::Confirm(const nsAString& aString, bool* aReturn)
   return rv.ErrorCode();
 }
 
+already_AddRefed<Promise>
+nsGlobalWindow::Fetch(const RequestOrScalarValueString& aInput,
+                      const RequestInit& aInit, ErrorResult& aRv)
+{
+  aRv.Throw(NS_ERROR_NOT_IMPLEMENTED);
+  return nullptr;
+}
+
 void
 nsGlobalWindow::Prompt(const nsAString& aMessage, const nsAString& aInitial,
                        nsAString& aReturn, ErrorResult& aError)
diff --git a/dom/base/nsGlobalWindow.h b/dom/base/nsGlobalWindow.h
index df3a119def27..a86310630a81 100644
--- a/dom/base/nsGlobalWindow.h
+++ b/dom/base/nsGlobalWindow.h
@@ -38,8 +38,10 @@
 #include "nsSize.h"
 #include "mozFlushType.h"
 #include "prclist.h"
+#include "mozilla/dom/RequestBinding.h"
 #include "mozilla/dom/StorageEvent.h"
 #include "mozilla/dom/StorageEventBinding.h"
+#include "mozilla/dom/UnionTypes.h"
 #include "nsFrameMessageManager.h"
 #include "mozilla/LinkedList.h"
 #include "mozilla/TimeStamp.h"
@@ -107,6 +109,7 @@ class MediaQueryList;
 class MozSelfSupport;
 class Navigator;
 class OwningExternalOrWindowProxy;
+class Promise;
 class Selection;
 class SpeechSynthesis;
 class WakeLock;
@@ -850,6 +853,9 @@ public:
   void Alert(mozilla::ErrorResult& aError);
   void Alert(const nsAString& aMessage, mozilla::ErrorResult& aError);
   bool Confirm(const nsAString& aMessage, mozilla::ErrorResult& aError);
+  already_AddRefed<mozilla::dom::Promise> Fetch(const mozilla::dom::RequestOrScalarValueString& aInput,
+                                                const mozilla::dom::RequestInit& aInit,
+                                                mozilla::ErrorResult& aRv);
   void Prompt(const nsAString& aMessage, const nsAString& aInitial,
               nsAString& aReturn, mozilla::ErrorResult& aError);
   void Print(mozilla::ErrorResult& aError);
diff --git a/dom/webidl/Fetch.webidl b/dom/webidl/Fetch.webidl
index 26c9775e696a..a1c66f3579d8 100644
--- a/dom/webidl/Fetch.webidl
+++ b/dom/webidl/Fetch.webidl
@@ -27,3 +27,10 @@ interface Body {
   [Throws]
   Promise<ScalarValueString> text();
 };
+
+[NoInterfaceObject, Exposed=(Window,Worker)]
+interface GlobalFetch {
+  [Throws, Func="mozilla::dom::Headers::PrefEnabled"]
+  Promise<Response> fetch(RequestInfo input, optional RequestInit init);
+};
+
diff --git a/dom/webidl/Window.webidl b/dom/webidl/Window.webidl
index 7bf30c1de773..2c6e2cc7e8b0 100644
--- a/dom/webidl/Window.webidl
+++ b/dom/webidl/Window.webidl
@@ -465,3 +465,4 @@ interface ChromeWindow {
 };
 
 Window implements ChromeWindow;
+Window implements GlobalFetch;
diff --git a/dom/webidl/WorkerGlobalScope.webidl b/dom/webidl/WorkerGlobalScope.webidl
index bc0b2135628e..bbd41aa5ef71 100644
--- a/dom/webidl/WorkerGlobalScope.webidl
+++ b/dom/webidl/WorkerGlobalScope.webidl
@@ -38,6 +38,7 @@ partial interface WorkerGlobalScope {
 
 WorkerGlobalScope implements WindowTimers;
 WorkerGlobalScope implements WindowBase64;
+WorkerGlobalScope implements GlobalFetch;
 
 // Not implemented yet: bug 1072107.
 // WorkerGlobalScope implements FontFaceSource;
diff --git a/dom/workers/WorkerScope.cpp b/dom/workers/WorkerScope.cpp
index df34df4798e3..3e63247261aa 100644
--- a/dom/workers/WorkerScope.cpp
+++ b/dom/workers/WorkerScope.cpp
@@ -303,6 +303,14 @@ WorkerGlobalScope::GetPerformance()
   return mPerformance;
 }
 
+already_AddRefed<Promise>
+WorkerGlobalScope::Fetch(const RequestOrScalarValueString& aInput,
+                         const RequestInit& aInit, ErrorResult& aRv)
+{
+  aRv.Throw(NS_ERROR_NOT_IMPLEMENTED);
+  return nullptr;
+}
+
 DedicatedWorkerGlobalScope::DedicatedWorkerGlobalScope(WorkerPrivate* aWorkerPrivate)
 : WorkerGlobalScope(aWorkerPrivate)
 {
diff --git a/dom/workers/WorkerScope.h b/dom/workers/WorkerScope.h
index a683e0670cc6..b522bfe1a237 100644
--- a/dom/workers/WorkerScope.h
+++ b/dom/workers/WorkerScope.h
@@ -8,6 +8,8 @@
 
 #include "Workers.h"
 #include "mozilla/DOMEventTargetHelper.h"
+#include "mozilla/dom/RequestBinding.h"
+#include "mozilla/dom/UnionTypes.h"
 
 namespace mozilla {
 namespace dom {
@@ -120,6 +122,9 @@ public:
   Dump(const Optional<nsAString>& aString) const;
 
   Performance* GetPerformance();
+
+  already_AddRefed<Promise>
+  Fetch(const RequestOrScalarValueString& aInput, const RequestInit& aInit, ErrorResult& aRv);
 };
 
 class DedicatedWorkerGlobalScope MOZ_FINAL : public WorkerGlobalScope
diff --git a/dom/workers/test/fetch/worker_interfaces.js b/dom/workers/test/fetch/worker_interfaces.js
index 7b2749807815..e3c2700fe0e8 100644
--- a/dom/workers/test/fetch/worker_interfaces.js
+++ b/dom/workers/test/fetch/worker_interfaces.js
@@ -7,5 +7,6 @@ onmessage = function() {
   ok(typeof Headers === "function", "Headers should be defined");
   ok(typeof Request === "function", "Request should be defined");
   ok(typeof Response === "function", "Response should be defined");
+  ok(typeof fetch === "function", "fetch() should be defined");
   postMessage({ type: 'finish' });
 }