HKX files store binary animation data and are associated with games developed by Bethesda Softworks, especially The Elder Scrolls V: Skyrim game released for consoles (Xbox 360 and PlayStation 3) and Windows PC in 2011.

Animations stored in HKX files are one of the fundamental elements of the game and thus such files must not be deleted by the user. However, HKX files can be replaced with modified HKX files distributed by Bethesda.