Ralph E. "Buckshot" O'Brien (April 8, 1928 – August 22, 2018) was an American professional basketball player.

A 5'9" point guard from Butler University, O'Brien played two seasons (1951–1953) in the National Basketball Association as a member of the Indianapolis Olympians and Baltimore Bullets.

He averaged 7.1 points per game in his NBA career.

[1] O'Brien was the last Butler product to appear in an NBA game for more than a half-century, before the 2010 arrival of Gordon Hayward.

This biographical article relating to a United States basketball player, coach, or other figure born in the 1920s is a stub.