Castle of Illusion Starring Mickey Mouse, known in Japan as I Love Mickey Mouse: Great Mysterious Castle Adventure (アイラブミッキーマウス ふしぎのお城大冒険, Ai Rabu Mikkī Mausu: Fushigi no Shiro Daibōken) is a video game first released in 1990 for the Sega Genesis which was developed by Sega of Japan. It is the first game in Sega's Illusion series of Mickey Mouse games. It was amongst the second wave of games initially released for the platform which helped seal the console's reputation within the period until the release of Sonic the Hedgehog.

The game is a side-scrolling game putting the player in control of Mickey. Each level exists within the large titular castle and the player must defeat enemies and bosses by jumping on them (similarly to most Mario platformers), or collecting apples and marbles to use as projectiles. The player can also collect icons to increase health, collect extra lives, or gain bonus points. After defeating a boss, the player is given a gem. When all seven gems are collected, the player can build a rainbow bridge that allows Mickey to walk into the castle's tower for a final battle against the witch, who in her youthful form resembles the The Evil Queen.