Frederick Aloys Hahn (February 16, 1929 – August 16, 1984) was an American professional baseball pitcher who worked in one game in Major League Baseball (MLB) for the St. Louis Cardinals in 1952.^[1] Despite his brief MLB tenure, Hahn, a left-hander from Nyack, New York, had a 13-year (1947–1959) professional career. He was listed as 6 feet 3 inches (1.91 m) tall and 174 pounds (79 kg).

In his lone big-league appearance, on April 19, 1952, at Wrigley Field, Hahn was called into the contest in the seventh inning with the Chicago Cubs in command, 6–0. He pitched the seventh and eighth innings and allowed two unearned runs, two hits and one base on balls.^[2] He spent the rest of 1952 at Triple-A Rochester.