diff --git a/dom/base/nsContentUtils.cpp b/dom/base/nsContentUtils.cpp
index 7706b8b45522..4062a63f1ceb 100644
--- a/dom/base/nsContentUtils.cpp
+++ b/dom/base/nsContentUtils.cpp
@@ -5397,8 +5397,7 @@ nsContentUtils::SetDataTransferInEvent(WidgetDragEvent* aDragEvent)
   }
 
   bool isCrossDomainSubFrameDrop = false;
-  if (aDragEvent->mMessage == eDrop ||
-      aDragEvent->mMessage == eLegacyDragDrop) {
+  if (aDragEvent->mMessage == eDrop) {
     isCrossDomainSubFrameDrop = CheckForSubFrameDrop(dragSession, aDragEvent);
   }
 
@@ -5422,7 +5421,6 @@ nsContentUtils::SetDataTransferInEvent(WidgetDragEvent* aDragEvent)
                                  FilterDropEffect(action, effectAllowed));
   }
   else if (aDragEvent->mMessage == eDrop ||
-           aDragEvent->mMessage == eLegacyDragDrop ||
            aDragEvent->mMessage == eDragEnd) {
     // For the drop and dragend events, set the drop effect based on the
     // last value that the dropEffect had. This will have been set in
diff --git a/dom/base/nsGkAtomList.h b/dom/base/nsGkAtomList.h
index ce7207ed0f74..7852d1e67e45 100644
--- a/dom/base/nsGkAtomList.h
+++ b/dom/base/nsGkAtomList.h
@@ -328,7 +328,6 @@ GK_ATOM(DOMNodeRemovedFromDocument, "DOMNodeRemovedFromDocument")
 GK_ATOM(DOMSubtreeModified, "DOMSubtreeModified")
 GK_ATOM(double_, "double")
 GK_ATOM(drag, "drag")
-GK_ATOM(dragdrop, "dragdrop")
 GK_ATOM(dragend, "dragend")
 GK_ATOM(dragenter, "dragenter")
 GK_ATOM(dragevent, "dragevent")
diff --git a/dom/events/DataTransfer.cpp b/dom/events/DataTransfer.cpp
index 62a8a0717fee..4dad80261e87 100644
--- a/dom/events/DataTransfer.cpp
+++ b/dom/events/DataTransfer.cpp
@@ -616,8 +616,7 @@ DataTransfer::GetDataAtInternal(const nsAString& aFormat, uint32_t aIndex,
   // we only allow access to data of the same principal. During other events,
   // only allow access to the data with the same principal.
   bool checkFormatItemPrincipal = mIsCrossDomainSubFrameDrop ||
-      (mEventMessage != eDrop && mEventMessage != eLegacyDragDrop &&
-       mEventMessage != ePaste);
+      (mEventMessage != eDrop && mEventMessage != ePaste);
   MOZ_ASSERT(aSubjectPrincipal);
 
   RefPtr<DataTransferItem> item = mItems->MozItemByTypeAt(format, aIndex);
diff --git a/dom/events/EventNameList.h b/dom/events/EventNameList.h
index a6be47dd88c4..7aee449e6c6d 100644
--- a/dom/events/EventNameList.h
+++ b/dom/events/EventNameList.h
@@ -774,10 +774,6 @@ NON_IDL_EVENT(dragexit,
               eDragExit,
               EventNameType_XUL,
               eDragEventClass)
-NON_IDL_EVENT(dragdrop,
-              eLegacyDragDrop,
-              EventNameType_XUL,
-              eDragEventClass)
 NON_IDL_EVENT(overflow,
               eScrollPortOverflow,
               EventNameType_XUL,
diff --git a/dom/plugins/base/nsPluginInstanceOwner.cpp b/dom/plugins/base/nsPluginInstanceOwner.cpp
index e43687cfdd55..3d8001f06e8a 100644
--- a/dom/plugins/base/nsPluginInstanceOwner.cpp
+++ b/dom/plugins/base/nsPluginInstanceOwner.cpp
@@ -2906,7 +2906,6 @@ nsPluginInstanceOwner::Destroy()
   content->RemoveEventListener(NS_LITERAL_STRING("keydown"), this, true);
   content->RemoveEventListener(NS_LITERAL_STRING("keyup"), this, true);
   content->RemoveEventListener(NS_LITERAL_STRING("drop"), this, true);
-  content->RemoveEventListener(NS_LITERAL_STRING("dragdrop"), this, true);
   content->RemoveEventListener(NS_LITERAL_STRING("drag"), this, true);
   content->RemoveEventListener(NS_LITERAL_STRING("dragenter"), this, true);
   content->RemoveEventListener(NS_LITERAL_STRING("dragover"), this, true);
@@ -3305,7 +3304,6 @@ nsresult nsPluginInstanceOwner::Init(nsIContent* aContent)
   aContent->AddEventListener(NS_LITERAL_STRING("keydown"), this, true);
   aContent->AddEventListener(NS_LITERAL_STRING("keyup"), this, true);
   aContent->AddEventListener(NS_LITERAL_STRING("drop"), this, true);
-  aContent->AddEventListener(NS_LITERAL_STRING("dragdrop"), this, true);
   aContent->AddEventListener(NS_LITERAL_STRING("drag"), this, true);
   aContent->AddEventListener(NS_LITERAL_STRING("dragenter"), this, true);
   aContent->AddEventListener(NS_LITERAL_STRING("dragover"), this, true);
diff --git a/widget/EventMessageList.h b/widget/EventMessageList.h
index b8e666d286d1..4d695544f521 100644
--- a/widget/EventMessageList.h
+++ b/widget/EventMessageList.h
@@ -131,7 +131,6 @@ NS_EVENT_MESSAGE(eBlur)
 NS_EVENT_MESSAGE(eDragEnter)
 NS_EVENT_MESSAGE(eDragOver)
 NS_EVENT_MESSAGE(eDragExit)
-NS_EVENT_MESSAGE(eLegacyDragDrop)
 NS_EVENT_MESSAGE(eDrag)
 NS_EVENT_MESSAGE(eDragEnd)
 NS_EVENT_MESSAGE(eDragStart)
diff --git a/widget/WidgetEventImpl.cpp b/widget/WidgetEventImpl.cpp
index 60c7dbb35af3..8a7b64cedbc0 100644
--- a/widget/WidgetEventImpl.cpp
+++ b/widget/WidgetEventImpl.cpp
@@ -213,7 +213,6 @@ WidgetEvent::HasDragEventMessage() const
     case eDragEnter:
     case eDragOver:
     case eDragExit:
-    case eLegacyDragDrop:
     case eDrag:
     case eDragEnd:
     case eDragStart: