W3X is an extension used by files associated with the expansion pack for the Warcraft III strategy game The Frozen Throne. W3X files are used to store custom game maps or other data used in the game. These can be objects placed on the map, military units or terrain. Such files are created by the game community using the Warcraft III World Editor or Frozen Throne Editor.

Warcraft III and The Frozen Throne expansion pack were developed by Blizzard Entertainment, Inc.