John Emmanuel Mahnken (June 16, 1922 – December 14, 2000) was an American professional basketball player. A 6'8" center from West New York, New Jersey, Mahnken played high school basketball at Memorial High School in his hometown. He played at Georgetown University during the early 1940s, earning All-American honors in 1943. He served in the United States Army from 1943 to 1945, then embarked on a professional career in the National Basketball League with the Rochester Royals. Mahnken won the 1946 league title on a Royals team which included future New York Knicks coach Red Holzman and future television actor Chuck Connors.