John Phalen "Stuffy" McInnis (September 19, 1890 – February 16, 1960) was a first baseman and manager in Major League Baseball.
McInnis gained his nickname as a youngster in the Boston suburban leagues, where his spectacular playing brought shouts of "that's the stuff, kid".
From 1909-27, McInnis played for the Philadelphia Athletics (1909–17), Boston Red Sox (1918–21), Cleveland Indians (1922), Boston Braves (1923–24), Pittsburgh Pirates (1925–26) and Philadelphia Phillies (1927). He batted and threw right-handed.