John O'Brien (May 21, 1960 – April 10, 1994) was an American author. His first novel Leaving Las Vegas was published in 1990 by Watermark Press and made into a film in 1995.

John Patrick O'Brien (born on August 29, 1977 in Los Angeles, California) is an American soccer player, one of the first Americans to earn a starting spot with a major European team, which he did with Ajax Amsterdam. United States teammate Landon Donovan called O'Brien the "best soccer player in the USA." http://fifaworldcup.yahoo.com/06/en/060502/1/6o8q.html He was released by C.D. Chivas USA of Major League Soccer following the 2006 season, making him eligible to play overseas without a transfer fee.

John O'Brien was a New Zealand political candidate and party leader.