Moo or MOO may refer to:
== In computing ==
MOO, a type of text-based online virtual reality system
MOO (programming language)
Moo.fx, a JavaScript effects library
Mode of operation in cryptography
== In entertainment and media ==
Moo (novel), by Jane Smiley
Moo, a number-guessing game, a computer variant of Bulls and Cows
MoO or Master of Orion, a computer game
Melody of Oblivion (MOO), an anime
Moo, a character in anime Monster Rancher
== People ==
Barbara E. Moo, American computer scientist
Douglas J. Moo, scholar who specialized in the New Testament
Eric Moo, singer and composer
Moo Ko-Suen...