--- a/dom/base/nsGlobalWindow.cpp
+++ b/dom/base/nsGlobalWindow.cpp
@@ -182,16 +182,17 @@
 #include "prlog.h"
 #include "prenv.h"
 #include "prprf.h"
 
 #include "mozilla/dom/MessageChannel.h"
 #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"
 
 #ifdef MOZ_GAMEPAD
 #include "mozilla/dom/GamepadService.h"
 #endif
 
 #include "nsRefreshDriver.h"
@@ -6365,16 +6366,24 @@ NS_IMETHODIMP
 nsGlobalWindow::Confirm(const nsAString& aString, bool* aReturn)
 {
   ErrorResult rv;
   *aReturn = Confirm(aString, rv);
 
   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)
 {
   // XXX This method is very similar to nsGlobalWindow::AlertOrConfirm, make
   // sure any modifications here don't need to happen over there!
   FORWARD_TO_OUTER_OR_THROW(Prompt, (aMessage, aInitial, aReturn, aError),
                             aError, );

--- a/dom/base/nsGlobalWindow.h
+++ b/dom/base/nsGlobalWindow.h
@@ -33,18 +33,20 @@
 #include "nsIScriptObjectPrincipal.h"
 #include "nsITimer.h"
 #include "nsIDOMModalContentWindow.h"
 #include "mozilla/EventListenerManager.h"
 #include "nsIPrincipal.h"
 #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"
 #include "nsWrapperCacheInlines.h"
 #include "nsIIdleObserver.h"
 #include "nsIDocument.h"
 #include "mozilla/dom/EventTarget.h"
 #include "mozilla/dom/WindowBinding.h"
@@ -102,16 +104,17 @@ class BarProp;
 class Console;
 class External;
 class Function;
 class Gamepad;
 class MediaQueryList;
 class MozSelfSupport;
 class Navigator;
 class OwningExternalOrWindowProxy;
+class Promise;
 class Selection;
 class SpeechSynthesis;
 class WakeLock;
 namespace indexedDB {
 class IDBFactory;
 } // namespace indexedDB
 } // namespace dom
 } // namespace mozilla
@@ -845,16 +848,19 @@ public:
 protected:
   bool AlertOrConfirm(bool aAlert, const nsAString& aMessage,
                       mozilla::ErrorResult& aError);
 
 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);
   void ShowModalDialog(JSContext* aCx, const nsAString& aUrl,
                        JS::Handle<JS::Value> aArgument,
                        const nsAString& aOptions,
                        JS::MutableHandle<JS::Value> aRetval,
                        mozilla::ErrorResult& aError);

--- a/dom/webidl/Fetch.webidl
+++ b/dom/webidl/Fetch.webidl
@@ -22,8 +22,15 @@ interface Body {
   Promise<Blob> blob();
   // FIXME(nsm): Bug 739173 FormData is not supported in workers.
   // Promise<FormData> formData();
   [Throws]
   Promise<JSON> json();
   [Throws]
   Promise<ScalarValueString> text();
 };
+
+[NoInterfaceObject, Exposed=(Window,Worker)]
+interface GlobalFetch {
+  [Throws, Func="mozilla::dom::Headers::PrefEnabled"]
+  Promise<Response> fetch(RequestInfo input, optional RequestInit init);
+};
+

--- a/dom/webidl/Window.webidl
+++ b/dom/webidl/Window.webidl
@@ -460,8 +460,9 @@ interface ChromeWindow {
    *
    * Throws NS_ERROR_NOT_IMPLEMENTED if the OS doesn't support this.
    */
   [Throws, Func="nsGlobalWindow::IsChromeWindow"]
   void beginWindowMove(Event mouseDownEvent, optional Element? panel = null);
 };
 
 Window implements ChromeWindow;
+Window implements GlobalFetch;

--- a/dom/webidl/WorkerGlobalScope.webidl
+++ b/dom/webidl/WorkerGlobalScope.webidl
@@ -33,16 +33,17 @@ partial interface WorkerGlobalScope {
   [Throws]
   void importScripts(DOMString... urls);
 
   readonly attribute WorkerNavigator navigator;
 };
 
 WorkerGlobalScope implements WindowTimers;
 WorkerGlobalScope implements WindowBase64;
+WorkerGlobalScope implements GlobalFetch;
 
 // Not implemented yet: bug 1072107.
 // WorkerGlobalScope implements FontFaceSource;
 
 // Mozilla extensions
 partial interface WorkerGlobalScope {
   attribute EventHandler onclose;
 

--- a/dom/workers/WorkerScope.cpp
+++ b/dom/workers/WorkerScope.cpp
@@ -298,16 +298,24 @@ WorkerGlobalScope::GetPerformance()
 
   if (!mPerformance) {
     mPerformance = new Performance(mWorkerPrivate);
   }
 
   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)
 {
 }
 
 JSObject*
 DedicatedWorkerGlobalScope::WrapGlobalObject(JSContext* aCx)
 {

--- a/dom/workers/WorkerScope.h
+++ b/dom/workers/WorkerScope.h
@@ -3,16 +3,19 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 #ifndef mozilla_dom_workerscope_h__
 #define mozilla_dom_workerscope_h__
 
 #include "Workers.h"
 #include "mozilla/DOMEventTargetHelper.h"
+#include "mozilla/dom/Headers.h"
+#include "mozilla/dom/RequestBinding.h"
+#include "mozilla/dom/UnionTypes.h"
 
 namespace mozilla {
 namespace dom {
 
 class Console;
 class Function;
 class Promise;
 
@@ -115,16 +118,19 @@ public:
   IMPL_EVENT_HANDLER(online)
   IMPL_EVENT_HANDLER(offline)
   IMPL_EVENT_HANDLER(close)
 
   void
   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
 {
   ~DedicatedWorkerGlobalScope() { }
 
 public:
   explicit DedicatedWorkerGlobalScope(WorkerPrivate* aWorkerPrivate);

--- a/dom/workers/test/fetch/worker_interfaces.js
+++ b/dom/workers/test/fetch/worker_interfaces.js
@@ -2,10 +2,11 @@ function ok(a, msg) {
   dump("OK: " + !!a + "  =>  " + a + " " + msg + "\n");
   postMessage({type: 'status', status: !!a, msg: a + ": " + msg });
 }
 
 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' });
 }