Slap Happy Lion is a 1947 American animated short film directed by Tex Avery and produced by Fred Quimby for Metro-Goldwyn-Mayer. Released on September 20, 1947, the short details the tragic downfall of a lion from king of the beasts to a gibbering, pill-popping wreck. It is narrated by a mouse whose torments drove him crazy. The mouse's voice was supplied by Frank Graham. Scott Bradley provided the music.

The closing title in the re-issued version does not display the regular MGM card, and erroneously uses the Tom and Jerry card instead. This might indicate that MGM made a mistake when reissuing it. Also, the Tom and Jerry short Smarty Cat also does not display the ending card, using the regular MGM card instead.

The lion's design served as the inspiration for the design of Genghis, a character from The Wacky World of Tex Avery. And also, his appearance of Tom and Jerry series in Jerry and The Lion.