Jack Wally McMahan (July 25, 1932 – October 16, 2020) was a right-handed batting, left-handed throwing Major League Baseball pitcher who played in 1956 for the Pittsburgh Pirates and Kansas City Athletics.

In eleven games with the Pirates, he posted a 6.08 ERA after allowing eighteen hits and nine earned runs in 131⁄3 innings of work.

On June 23, he was traded by the Pirates with Curt Roberts to the Athletics for Spook Jacobs.

On February 19, 1957, the Athletics — with players to be named later, Wayne Belardi, Art Ditmar, and Bobby Shantz — sent McMahan to the Yankees for a player to be named later, Irv Noren, Milt Graff, Mickey McDermott, Tom Morgan, Rip Coleman, and Billy Hunter.

The Athletics sent Curt Roberts and Clete Boyer to the Yankees to complete the trade.