Warren Louis Hacker (November 21, 1924 – May 22, 2002) was an American professional baseball player, a pitcher for the Chicago Cubs (1948–56), Cincinnati Redlegs (1957), Philadelphia Phillies (1957–58) and Chicago White Sox (1961).

[1] He was also the uncle of former Major League shortstop Rich Hacker.

Hacker's finished 23rd in voting for the National League Most Valuable Player Award in 1952 for leading the league in WHIP (.946) and hits allowed/9ip (7.01) and having a 15–9 win–loss record, 33 games pitched (20 started), 12 complete games, 5 shutouts, 5 games finished, 1 save, 185 innings pitched, 144 hits allowed, 56 runs allowed, 53 earned runs allowed, 17 home runs allowed, 31 walks allowed, 84 strikeouts, 1 hit batsmen, 1 wild pitch, 721 batters faced, 1 balk and a 2.58 ERA.

After leaving the major leagues in 1961, Hacker played for the Indianapolis Indians from 1962 to 1965, which he recalled as "maybe the best days I ever had in baseball.

This biographical article relating to an American baseball pitcher born in the 1920s is a stub.