Alex Kidd in the Enchanted Castle (アレックスキッド 天空魔城) is a side-scrolling platform game developed and published by Sega for the Sega Genesis video game console. The game was released in Japan in February 1989, in the U.S. in January 1990 and in Europe on November 1990. It is the only 16-bit platform game starring Alex Kidd, and the fifth game in the Alex Kidd series of video games.

Alex Kidd in the Enchanted Castle follows Alex as he fights his way through the fictional planet Paperock in search of his long-lost father, King Thor. Alex has access to several items and vehicles that help him complete his quest, including a motorbike, pedicopter, and pogo stick, which each give him unique abilities. While traveling through eleven worlds, Alex must defeat several opponents in rock-paper-scissors before finally finding King Thor.

The player guides Alex through eleven stages by fighting and avoiding enemies and obstacles. Alex can jump, kick, crawl or punch enemies, causing them to explode into gold coins, called Baums. New items and vehicles are gained by playing Janken (Rock, Paper, Scissors) in gambling houses, including the Sukopako Motorcycle, the pedicopter (a small pedal-powered helicopter), a pogo stick and wizard cane which allows Alex to float in the air for a few seconds. One hit from any enemy causes Alex to die instantly.

In the original Japanese version of the game, when Alex or his opponent lose a Rock Paper Scissors match, the loser's clothes disappear, leaving him/her naked with a fig leaf over his/her genitalia. In the Western versions, the loser is flattened by a heavy weight. Several levels were also renamed for the Western release.