--- a/accessible/base/AccEvent.cpp
+++ b/accessible/base/AccEvent.cpp
@@ -257,12 +257,20 @@ already_AddRefed<nsIAccessibleEvent> a11
   if (eventGroup & (1 << AccEvent::eScrollingEvent)) {
     AccScrollingEvent* sa = downcast_accEvent(aEvent);
     xpEvent = new xpcAccScrollingEvent(
         type, ToXPC(acc), ToXPCDocument(doc), node, fromUser, sa->ScrollX(),
         sa->ScrollY(), sa->MaxScrollX(), sa->MaxScrollY());
     return xpEvent.forget();
   }
 
+  if (eventGroup & (1 << AccEvent::eAnnouncementEvent)) {
+    AccAnnouncementEvent* aa = downcast_accEvent(aEvent);
+    xpEvent = new xpcAccAnnouncementEvent(type, ToXPC(acc), ToXPCDocument(doc),
+                                          node, fromUser, aa->Announcement(),
+                                          aa->Priority());
+    return xpEvent.forget();
+  }
+
   xpEvent =
       new xpcAccEvent(type, ToXPC(acc), ToXPCDocument(doc), node, fromUser);
   return xpEvent.forget();
 }

--- a/accessible/base/AccEvent.h
+++ b/accessible/base/AccEvent.h
@@ -99,16 +99,17 @@ class AccEvent {
     eShowEvent,
     eCaretMoveEvent,
     eTextSelChangeEvent,
     eSelectionChangeEvent,
     eTableChangeEvent,
     eVirtualCursorChangeEvent,
     eObjectAttrChangedEvent,
     eScrollingEvent,
+    eAnnouncementEvent,
   };
 
   static const EventGroup kEventGroup = eGenericEvent;
   virtual unsigned int GetEventGroups() const { return 1U << eGenericEvent; }
 
   /**
    * Reference counting and cycle collection.
    */
@@ -540,16 +541,44 @@ class AccScrollingEvent : public AccEven
  private:
   uint32_t mScrollX;
   uint32_t mScrollY;
   uint32_t mMaxScrollX;
   uint32_t mMaxScrollY;
 };
 
 /**
+ * Accessible announcement event.
+ */
+class AccAnnouncementEvent : public AccEvent {
+ public:
+  AccAnnouncementEvent(Accessible* aAccessible, const nsAString& aAnnouncement,
+                       uint16_t aPriority)
+      : AccEvent(nsIAccessibleEvent::EVENT_ANNOUNCEMENT, aAccessible),
+        mAnnouncement(aAnnouncement),
+        mPriority(aPriority) {}
+
+  virtual ~AccAnnouncementEvent() {}
+
+  // AccEvent
+  static const EventGroup kEventGroup = eAnnouncementEvent;
+  virtual unsigned int GetEventGroups() const override {
+    return AccEvent::GetEventGroups() | (1U << eAnnouncementEvent);
+  }
+
+  const nsString& Announcement() const { return mAnnouncement; }
+
+  uint16_t Priority() { return mPriority; }
+
+ private:
+  nsString mAnnouncement;
+  uint16_t mPriority;
+};
+
+/**
  * Downcast the generic accessible event object to derived type.
  */
 class downcast_accEvent {
  public:
   explicit downcast_accEvent(AccEvent* e) : mRawPtr(e) {}
 
   template <class Destination>
   operator Destination*() {

--- a/accessible/base/nsAccessibilityService.h
+++ b/accessible/base/nsAccessibilityService.h
@@ -460,11 +460,12 @@ static const char kEventTypeNames[][40] 
     "hypertext link selected",          // EVENT_HYPERTEXT_LINK_SELECTED
     "hyperlink start index changed",    // EVENT_HYPERLINK_START_INDEX_CHANGED
     "hypertext changed",                // EVENT_HYPERTEXT_CHANGED
     "hypertext links count changed",    // EVENT_HYPERTEXT_NLINKS_CHANGED
     "object attribute changed",         // EVENT_OBJECT_ATTRIBUTE_CHANGED
     "virtual cursor changed",           // EVENT_VIRTUALCURSOR_CHANGED
     "text value change",                // EVENT_TEXT_VALUE_CHANGE
     "scrolling",                        // EVENT_SCROLLING
+    "announcement",                     // EVENT_ANNOUNCEMENT
 };
 
 #endif

--- a/accessible/generic/Accessible.cpp
+++ b/accessible/generic/Accessible.cpp
@@ -2436,16 +2436,22 @@ Accessible* Accessible::ContainerWidget(
 
       // Don't cross DOM document boundaries.
       if (parent->IsDoc()) break;
     }
   }
   return nullptr;
 }
 
+void Accessible::Announce(const nsAString& aAnnouncement, uint16_t aPriority) {
+  RefPtr<AccAnnouncementEvent> event =
+      new AccAnnouncementEvent(this, aAnnouncement, aPriority);
+  nsEventShell::FireEvent(event);
+}
+
 ////////////////////////////////////////////////////////////////////////////////
 // Accessible protected methods
 
 void Accessible::LastRelease() {
   // First cleanup if needed...
   if (mDoc) {
     Shutdown();
     NS_ASSERTION(!mDoc,

--- a/accessible/generic/Accessible.h
+++ b/accessible/generic/Accessible.h
@@ -975,16 +975,18 @@ class Accessible : public nsISupports {
    */
   void SetShowEventTarget(bool aTarget) { mShowEventTarget = aTarget; }
 
   /**
    * Set if this accessible is a hide event target.
    */
   void SetHideEventTarget(bool aTarget) { mHideEventTarget = aTarget; }
 
+  void Announce(const nsAString& aAnnouncement, uint16_t aPriority);
+
  protected:
   virtual ~Accessible();
 
   /**
    * Return the accessible name provided by native markup. It doesn't take
    * into account ARIA markup used to specify the name.
    */
   virtual mozilla::a11y::ENameValueFlag NativeName(nsString& aName) const;

--- a/accessible/interfaces/moz.build
+++ b/accessible/interfaces/moz.build
@@ -5,16 +5,17 @@
 # file, You can obtain one at http://mozilla.org/MPL/2.0/.
 
 if CONFIG['MOZ_WIDGET_TOOLKIT'] == 'windows' and CONFIG['COMPILE_ENVIRONMENT']:
     DIRS += ['gecko', 'msaa', 'ia2']
 
 XPIDL_SOURCES += [
     'nsIAccessibilityService.idl',
     'nsIAccessible.idl',
+    'nsIAccessibleAnnouncementEvent.idl',
     'nsIAccessibleApplication.idl',
     'nsIAccessibleCaretMoveEvent.idl',
     'nsIAccessibleDocument.idl',
     'nsIAccessibleEditableText.idl',
     'nsIAccessibleEvent.idl',
     'nsIAccessibleHideEvent.idl',
     'nsIAccessibleHyperLink.idl',
     'nsIAccessibleHyperText.idl',

--- a/accessible/interfaces/nsIAccessible.idl
+++ b/accessible/interfaces/nsIAccessible.idl
@@ -293,14 +293,24 @@ interface nsIAccessible : nsISupports
    * @param coordinateType [in] - specifies whether the coordinates are relative to
    *                         the screen or the parent object (for available
    *                         constants refer to nsIAccessibleCoordinateType)
    * @param x [in] - defines the x coordinate
    * @param y [in] - defines the y coordinate
   */
   void scrollToPoint(in unsigned long coordinateType, in long x, in long y);
 
+  /**
+   * Dispatches an ANNOUNCEMENT event with this accessible as target.
+   *
+   * @param announcement [in] - string to use in announcement.
+   * @param priority [in] - priority for announcement, could be
+   *                      nsIAccessibleAnnouncementEvent.POLITE or
+   *                      nsIAccessibleAnnouncementEvent.ASSERTIVE.
+   */
+  void announce(in AString announcement, in unsigned short priority);
+
   %{C++
   virtual mozilla::a11y::Accessible* ToInternalAccessible() const = 0;
   %}
 
 };
 

new file mode 100644
--- /dev/null
+++ b/accessible/interfaces/nsIAccessibleAnnouncementEvent.idl
@@ -0,0 +1,23 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * 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/. */
+
+#include "nsIAccessibleEvent.idl"
+
+/**
+ * Fired when announce() is called on the target accessible.
+ */
+[scriptable, builtinclass, uuid(8818e49c-1286-4fe6-ae82-4d1b795ec88d)]
+interface nsIAccessibleAnnouncementEvent : nsIAccessibleEvent
+{
+  const unsigned short POLITE = 0;
+  const unsigned short ASSERTIVE = 1;
+
+  // String of actual announcement
+  readonly attribute AString announcement;
+
+  // Priority for announcement, could be POLITE or ASSERTIVE, ATs
+  // will decide how to appropriately present it.
+  readonly attribute unsigned short priority;
+};

--- a/accessible/interfaces/nsIAccessibleEvent.idl
+++ b/accessible/interfaces/nsIAccessibleEvent.idl
@@ -419,19 +419,24 @@ interface nsIAccessibleEvent : nsISuppor
   const unsigned long EVENT_TEXT_VALUE_CHANGE = 0x0057;
 
   /**
    * An accessible's viewport is scrolling.
    */
   const unsigned long EVENT_SCROLLING = 0x0058;
 
   /**
+   * An accessible is making an explicit announcement.
+   */
+  const unsigned long EVENT_ANNOUNCEMENT = 0x0059;
+
+  /**
    * Help make sure event map does not get out-of-line.
    */
-  const unsigned long EVENT_LAST_ENTRY = 0x0059;
+  const unsigned long EVENT_LAST_ENTRY = 0x005A;
 
   /**
    * The type of event, based on the enumerated event values
    * defined in this interface.
    */
   readonly attribute unsigned long eventType;
   
   /**

--- a/accessible/tests/mochitest/common.js
+++ b/accessible/tests/mochitest/common.js
@@ -11,16 +11,18 @@ const nsIAccessibleCaretMoveEvent =
 const nsIAccessibleScrollingEvent =
   Ci.nsIAccessibleScrollingEvent;
 const nsIAccessibleTextChangeEvent =
   Ci.nsIAccessibleTextChangeEvent;
 const nsIAccessibleVirtualCursorChangeEvent =
   Ci.nsIAccessibleVirtualCursorChangeEvent;
 const nsIAccessibleObjectAttributeChangedEvent =
   Ci.nsIAccessibleObjectAttributeChangedEvent;
+const nsIAccessibleAnnouncementEvent =
+  Ci.nsIAccessibleAnnouncementEvent;
 
 const nsIAccessibleStates = Ci.nsIAccessibleStates;
 const nsIAccessibleRole = Ci.nsIAccessibleRole;
 const nsIAccessibleScrollType = Ci.nsIAccessibleScrollType;
 const nsIAccessibleCoordinateType = Ci.nsIAccessibleCoordinateType;
 
 const nsIAccessibleRelation = Ci.nsIAccessibleRelation;
 const nsIAccessibleTextRange = Ci.nsIAccessibleTextRange;

--- a/accessible/tests/mochitest/events.js
+++ b/accessible/tests/mochitest/events.js
@@ -1,15 +1,16 @@
 // XXX Bug 1425371 - enable no-redeclare and fix the issues with the tests.
 /* eslint-disable no-redeclare */
 
 // //////////////////////////////////////////////////////////////////////////////
 // Constants
 
 const EVENT_ALERT = nsIAccessibleEvent.EVENT_ALERT;
+const EVENT_ANNOUNCEMENT = nsIAccessibleEvent.EVENT_ANNOUNCEMENT;
 const EVENT_DESCRIPTION_CHANGE = nsIAccessibleEvent.EVENT_DESCRIPTION_CHANGE;
 const EVENT_DOCUMENT_LOAD_COMPLETE = nsIAccessibleEvent.EVENT_DOCUMENT_LOAD_COMPLETE;
 const EVENT_DOCUMENT_RELOAD = nsIAccessibleEvent.EVENT_DOCUMENT_RELOAD;
 const EVENT_DOCUMENT_LOAD_STOPPED = nsIAccessibleEvent.EVENT_DOCUMENT_LOAD_STOPPED;
 const EVENT_HIDE = nsIAccessibleEvent.EVENT_HIDE;
 const EVENT_FOCUS = nsIAccessibleEvent.EVENT_FOCUS;
 const EVENT_NAME_CHANGE = nsIAccessibleEvent.EVENT_NAME_CHANGE;
 const EVENT_MENU_START = nsIAccessibleEvent.EVENT_MENU_START;

--- a/accessible/tests/mochitest/events/a11y.ini
+++ b/accessible/tests/mochitest/events/a11y.ini
@@ -1,15 +1,16 @@
 [DEFAULT]
 support-files =
   focus.html
   scroll.html
   !/accessible/tests/mochitest/*.js
   !/accessible/tests/mochitest/letters.gif
 
+[test_announcement.html]
 [test_aria_alert.html]
 [test_aria_menu.html]
 [test_aria_objattr.html]
 [test_aria_owns.html]
 [test_aria_statechange.html]
 [test_attrs.html]
 [test_bug1322593.html]
 [test_bug1322593-2.html]

new file mode 100644
--- /dev/null
+++ b/accessible/tests/mochitest/events/test_announcement.html
@@ -0,0 +1,62 @@
+<html>
+
+<head>
+  <title>Announcement event and method testing</title>
+
+  <link rel="stylesheet" type="text/css"
+        href="chrome://mochikit/content/tests/SimpleTest/test.css" />
+
+  <script type="application/javascript"
+          src="chrome://mochikit/content/tests/SimpleTest/SimpleTest.js"></script>
+
+  <script type="application/javascript"
+          src="../common.js"></script>
+  <script type="application/javascript"
+          src="../role.js"></script>
+  <script type="application/javascript"
+          src="../states.js"></script>
+  <script type="application/javascript"
+          src="../events.js"></script>
+
+  <script type="application/javascript">
+    async function doTests() {
+      let acc = getAccessible("display");
+
+      let onAnnounce = waitForEventPromise(EVENT_ANNOUNCEMENT, acc);
+      acc.announce("please", nsIAccessibleAnnouncementEvent.POLITE);
+      let evt = await onAnnounce;
+      evt.QueryInterface(nsIAccessibleAnnouncementEvent);
+      is(evt.announcement, "please", "announcement matches.");
+      is(evt.priority, nsIAccessibleAnnouncementEvent.POLITE, "priority matches");
+
+      onAnnounce = waitForEventPromise(EVENT_ANNOUNCEMENT, acc);
+      acc.announce("do it", nsIAccessibleAnnouncementEvent.ASSERTIVE);
+      evt = await onAnnounce;
+      evt.QueryInterface(nsIAccessibleAnnouncementEvent);
+      is(evt.announcement, "do it", "announcement matches.");
+      is(evt.priority, nsIAccessibleAnnouncementEvent.ASSERTIVE,
+        "priority matches");
+
+      SimpleTest.finish();
+    }
+
+    SimpleTest.waitForExplicitFinish();
+    addA11yLoadEvent(doTests);
+  </script>
+</head>
+
+<body>
+
+  <a target="_blank"
+     href="https://bugzilla.mozilla.org/show_bug.cgi?id=1525980"
+     title="Introduce announcement event and method">
+    Mozilla Bug 1525980
+  </a>
+
+  <p id="display"></p>
+  <div id="content" style="display: none"></div>
+  <pre id="test">
+  </pre>
+
+</body>
+</html>

--- a/accessible/windows/msaa/nsEventMap.h
+++ b/accessible/windows/msaa/nsEventMap.h
@@ -96,10 +96,11 @@ static const uint32_t gWinEventMap[] = {
   IA2_EVENT_HYPERTEXT_LINK_SELECTED,                 // nsIAccessibleEvent::EVENT_HYPERTEXT_LINK_SELECTED
   IA2_EVENT_HYPERLINK_START_INDEX_CHANGED,           // nsIAccessibleEvent::EVENT_HYPERLINK_START_INDEX_CHANGED
   IA2_EVENT_HYPERTEXT_CHANGED,                       // nsIAccessibleEvent::EVENT_HYPERTEXT_CHANGED
   IA2_EVENT_HYPERTEXT_NLINKS_CHANGED,                // nsIAccessibleEvent::EVENT_HYPERTEXT_NLINKS_CHANGED
   IA2_EVENT_OBJECT_ATTRIBUTE_CHANGED,                // nsIAccessibleEvent::EVENT_OBJECT_ATTRIBUTE_CHANGED
   kEVENT_WIN_UNKNOWN,                                // nsIAccessibleEvent::EVENT_VIRTUALCURSOR_CHANGED
   EVENT_OBJECT_VALUECHANGE,                          // nsIAccessibleEvent::EVENT_TEXT_VALUE_CHANGE
   kEVENT_WIN_UNKNOWN,                                // nsIAccessibleEvent::EVENT_SCROLLING
+  kEVENT_WIN_UNKNOWN,                                // nsIAccessibleEvent::EVENT_ANNOUNCEMENT
     // clang-format on
 };

--- a/accessible/xpcom/AccEvents.conf
+++ b/accessible/xpcom/AccEvents.conf
@@ -10,10 +10,11 @@ simple_events = [
     'Event',
     'StateChangeEvent',
     'TextChangeEvent',
     'HideEvent',
     'CaretMoveEvent',
     'ObjectAttributeChangedEvent',
     'TableChangeEvent',
     'VirtualCursorChangeEvent',
-    'ScrollingEvent'
+    'ScrollingEvent',
+    'AnnouncementEvent'
   ]

--- a/accessible/xpcom/xpcAccessible.cpp
+++ b/accessible/xpcom/xpcAccessible.cpp
@@ -752,8 +752,18 @@ xpcAccessible::ScrollToPoint(uint32_t aC
     proxy->ScrollToPoint(aCoordinateType, aX, aY);
 #endif
   } else {
     Intl()->ScrollToPoint(aCoordinateType, aX, aY);
   }
 
   return NS_OK;
 }
+
+NS_IMETHODIMP
+xpcAccessible::Announce(const nsAString& aAnnouncement, uint16_t aPriority) {
+  if (IntlGeneric().IsProxy()) {
+    return NS_ERROR_NOT_IMPLEMENTED;
+  } else {
+    Intl()->Announce(aAnnouncement, aPriority);
+  }
+  return NS_OK;
+}

--- a/accessible/xpcom/xpcAccessible.h
+++ b/accessible/xpcom/xpcAccessible.h
@@ -77,16 +77,18 @@ class xpcAccessible : public nsIAccessib
   NS_IMETHOD GetActionDescription(uint8_t aIndex,
                                   nsAString& aDescription) final;
   NS_IMETHOD DoAction(uint8_t aIndex) final;
 
   NS_IMETHOD ScrollTo(uint32_t aHow) final;
   NS_IMETHOD ScrollToPoint(uint32_t aCoordinateType, int32_t aX,
                            int32_t aY) final;
 
+  NS_IMETHOD Announce(const nsAString& aAnnouncement, uint16_t aPriority) final;
+
  protected:
   xpcAccessible() {}
   virtual ~xpcAccessible() {}
 
  private:
   Accessible* Intl();
   AccessibleOrProxy IntlGeneric();