The 1971 U.S. Open was the 71st U.S. Open, held June 17–21 at the East Course of Merion Golf Club in Ardmore, Pennsylvania, a suburb west of Philadelphia. Lee Trevino, the 1968 champion, won his second U.S. Open, defeating Jack Nicklaus by three strokes in an 18-hole playoff. It was the second of Trevino's six major titles and the second of four times in which Nicklaus was the runner-up to Trevino in a major; Nicklaus won his third U.S. Open the following year.