The WII extension is used in files associated with the Ninetendo Wii game console. The disks on which the games for Ninetedo were stored were used to generate WII files. It was an encoded disc image. It is a binary disk image. This allowed for the backup of the game media. WII files were supported by Rawdump.

Currently, the WII format is rarely used and is considered obsolete. Sometimes used by Wii emulators such as Dolphin.