In multiplayer online games, a MUSH (a backronymed pun on MUD most often expanded as Multi-User Shared Hallucination, though Multi-User Shared Hack, Habitat, and Holodeck are also observed) is a text-based online social medium to which multiple users are connected at the same time. MUSHes are often used for online social intercourse and role-playing games, although the first forms of MUSH do not appear to be coded specifically to implement gaming activity. MUSH software was originally derived from MUDs; today's two major MUSH variants are descended from TinyMUD, which was fundamentally a social game. MUSH has forked over the years and there are now different varieties with different features, although most have strong similarities and one who is fluent in coding one variety can switch to coding for the other with only a little effort. The source code for most widely used MUSH servers is open source and available from its current maintainers.

Mush may refer to:
Mush, MUSH, or Mushing may also refer to:

• mush (cornmeal), a kind of corn pudding or porridge
• Mushing, a sport or transport method powered by dogs or a command to a dog team