Pat O'Brien (November 11, 1899 – October 15, 1983) was an American movie actor with over 100 screen credits. O'Brien was born William Joseph Patrick O'Brien to an Irish American Catholic family in Milwaukee, Wisconsin. He served as an altar boy at Gesu Church while growing up near 13th and Clybourn streets. O'Brien attended Marquette Academy with fellow actor Spencer Tracy, and later attended Marquette University. Reportedly he also served with Jack Benny at Great Lakes Naval Station during World War I.
O'Brien appeared with James Cagney in eight movies including Angels with Dirty Faces (1938) and Cagney's last film Ragtime (1981). He began appearing in movies (many times playing Irish cops or priests) in the 1930s, starting with the role of ace reporter Hildy Johnson in the original version of The Front Page in 1931. He memorably appeared in the highly successful 1946 suspense film, Crack-Up and played the lead in The Personality Kid.
He may be best remembered for his role as a police detective opposite George Raft in Some Like It Hot and the title role as a football coach in Knute Rockne, All American (1940), where he gave the speech to "win just one for the Gipper," referring to recently deceased football player George Gipp, portrayed in the film by a young Ronald Reagan (the origin of countless later references to President Reagan as "the Gipper"). O'Brien's movie career more or less ended in the early 1950s when he was apparently partially blacklisted for being a political conservative. He still did manage to get work in television; O'Brien later claimed to be completely flummoxed about this in his autobiography The Wind At My Back. His close friend Spencer Tracy had to fight the studio to get a small role for O'Brien in Tracy's film The Last Hurrah in 1958. O'Brien did have a small role as Burt Reynolds' father in Reynold's 1978 comedy film The End; veteran actress Myrna Loy played Reynolds' mother in the film.
O'Brien died from a heart attack at the age of 83.