diff --git a/dom/base/nsDeprecatedOperationList.h b/dom/base/nsDeprecatedOperationList.h
index adcf4d9d8202..1c9389f69bff 100644
--- a/dom/base/nsDeprecatedOperationList.h
+++ b/dom/base/nsDeprecatedOperationList.h
@@ -34,7 +34,6 @@ DEPRECATED_OPERATION(UseOfReleaseEvents)
 DEPRECATED_OPERATION(UseOfDOM3LoadMethod)
 DEPRECATED_OPERATION(ChromeUseOfDOM3LoadMethod)
 DEPRECATED_OPERATION(ShowModalDialog)
-DEPRECATED_OPERATION(Window_Content)
 DEPRECATED_OPERATION(SyncXMLHttpRequest)
 DEPRECATED_OPERATION(Window_Cc_ontrollers)
 DEPRECATED_OPERATION(ImportXULIntoContent)
diff --git a/dom/base/nsGlobalWindow.h b/dom/base/nsGlobalWindow.h
index 25433101263b..66af9852f9f9 100644
--- a/dom/base/nsGlobalWindow.h
+++ b/dom/base/nsGlobalWindow.h
@@ -1234,17 +1234,6 @@ public:
     return win.forget();
   }
 
-  void Get_content(JSContext* aCx,
-                   JS::MutableHandle<JSObject*> aRetval,
-                   mozilla::dom::SystemCallerGuarantee aCallerType,
-                   mozilla::ErrorResult& aError)
-  {
-    if (mDoc) {
-      mDoc->WarnOnceAbout(nsIDocument::eWindow_Content);
-    }
-    GetContent(aCx, aRetval, aCallerType, aError);
-  }
-
   already_AddRefed<mozilla::dom::Promise>
   CreateImageBitmap(JSContext* aCx,
                     const mozilla::dom::ImageBitmapSource& aImage,
diff --git a/dom/locales/en-US/chrome/dom/dom.properties b/dom/locales/en-US/chrome/dom/dom.properties
index ac9dbed58e08..3a750ecfa6d4 100644
--- a/dom/locales/en-US/chrome/dom/dom.properties
+++ b/dom/locales/en-US/chrome/dom/dom.properties
@@ -181,8 +181,6 @@ UseOfReleaseEventsWarning=Use of releaseEvents() is deprecated. To upgrade your
 UseOfDOM3LoadMethodWarning=Use of document.load() is deprecated. To upgrade your code, use the DOM XMLHttpRequest object. For more help https://developer.mozilla.org/en/XMLHttpRequest
 # LOCALIZATION NOTE: Do not translate "window.showModalDialog()" or "window.open()"
 ShowModalDialogWarning=Use of window.showModalDialog() is deprecated. Use window.open() instead. For more help https://developer.mozilla.org/en-US/docs/Web/API/Window.open
-# LOCALIZATION NOTE: Do not translate "window._content" or "window.content"
-Window_ContentWarning=window._content is deprecated.  Please use window.content instead.
 # LOCALIZATION NOTE: Do not translate "XMLHttpRequest"
 SyncXMLHttpRequestWarning=Synchronous XMLHttpRequest on the main thread is deprecated because of its detrimental effects to the end user’s experience. For more help http://xhr.spec.whatwg.org/
 ImplicitMetaViewportTagFallback=No meta-viewport tag found. Please explicitly specify one to prevent unexpected behavioural changes in future versions. For more help https://developer.mozilla.org/en/docs/Mozilla/Mobile/Viewport_meta_tag
diff --git a/dom/tests/browser/browser.ini b/dom/tests/browser/browser.ini
index 604f07bc7989..f937809c281c 100644
--- a/dom/tests/browser/browser.ini
+++ b/dom/tests/browser/browser.ini
@@ -55,7 +55,6 @@ skip-if = !e10s || (os == "win" && processor == "x86") # Large-Allocation requir
 [browser_localStorage_e10s.js]
 skip-if = !e10s # This is a test of e10s functionality.
 [browser_localStorage_privatestorageevent.js]
-[browser_test__content.js]
 [browser_test_focus_after_modal_state.js]
 support-files =
   focus_after_prompt.html
diff --git a/dom/tests/browser/browser_test__content.js b/dom/tests/browser/browser_test__content.js
deleted file mode 100644
index b06233527683..000000000000
--- a/dom/tests/browser/browser_test__content.js
+++ /dev/null
@@ -1,4 +0,0 @@
-function test() {
-    is(window._content, window.content,
-       "_content needs to work, since extensions use it");
-}
diff --git a/dom/webidl/Window.webidl b/dom/webidl/Window.webidl
index 6ee95703f0f1..a089aad25e2b 100644
--- a/dom/webidl/Window.webidl
+++ b/dom/webidl/Window.webidl
@@ -338,8 +338,6 @@ partial interface Window {
 
   [ChromeOnly, Replaceable, Throws, NeedsCallerType] readonly attribute object? content;
 
-  [ChromeOnly, Throws, NeedsCallerType] readonly attribute object? __content;
-
   [Throws, ChromeOnly] any getInterface(IID iid);
 
   /**
diff --git a/toolkit/components/addoncompat/RemoteAddonsParent.jsm b/toolkit/components/addoncompat/RemoteAddonsParent.jsm
index d640c47d31f8..a43f3411c20f 100644
--- a/toolkit/components/addoncompat/RemoteAddonsParent.jsm
+++ b/toolkit/components/addoncompat/RemoteAddonsParent.jsm
@@ -1017,10 +1017,7 @@ TabBrowserElementInterposition.methods.removeTabsProgressListener = function(add
 var ChromeWindowInterposition = new Interposition("ChromeWindowInterposition",
                                                   EventTargetInterposition);
 
-// _content is for older add-ons like pinboard and all-in-one gestures
-// that should be using content instead.
-ChromeWindowInterposition.getters.content =
-ChromeWindowInterposition.getters._content = function(addon, target) {
+ChromeWindowInterposition.getters.content = function(addon, target) {
   CompatWarning.warn("Direct access to chromeWindow.content will no longer work in the chrome process.",
                      addon, CompatWarning.warnings.content);