Robert Clayton Shantz (born September 26, 1925 in Pottstown, Pennsylvania) was a Major League Baseball pitcher for the Philadelphia Athletics (1949–1954), Kansas City Athletics (1955–1956), New York Yankees (1957–1960), Pittsburgh Pirates (1961), Houston Colt .45's (1962), St. Louis Cardinals (1962–1964), Chicago Cubs (1964), and the Philadelphia Phillies (1964).

A left-hander, Shantz began his career as a starting pitcher, but about halfway through he converted to a competent relief pitcher. In 1951 he added the knuckleball to his repertoire.

He enjoyed his best season in 1952 when he led the American League in wins (24) and won the MVP Award. In the process, he led the A's to their last winning season in Philadelphia. The 1952 A's had some excellent players, including batting champion Ferris Fain, home run hitter Gus Zernial, and fleet center fielder Dave Philly. But the club resumed its losing ways, drew fewer and fewer fans, and moved to Kansas City after the 1954 campaign.

A highly skilled fielder, Shantz won eight consecutive Gold Glove Awards from 1957 to 1964 (American League, 1957–60; National League, 1961–64; in 1957 the award was rendered for both leagues). Shantz also was selected for the All-Star Game in 1951, 1952 and 1957. In the fifth and final inning of the 1952 All Star Game, the left–handed Shantz exhibited his distinctive sidearm delivery and sharp curve. He struck out three respected hitters in a row: Whitey Lockman, Jackie Robinson, and Stan Musial.