Allen Lee Geiberger, Sr. (born September 1, 1937) is an American professional golfer who has won numerous golf tournaments.
Geiberger was born in Red Bluff, California. He graduated from the University of Southern California in 1959 and turned professional soon after.
Geiberger won eleven times on the PGA Tour, with victories that included one major championship, the 1966 PGA Championship, and the "near-major" 1975 Tournament Players Championship. He played on the 1967 and 1975 Ryder Cup teams. He also won ten times on the Senior PGA Tour (now called the Champions Tour).
On June 10, 1977, in the second round of the Danny Thomas Memphis Classic played at the Colonial Country Club in Cordova, Tennessee, he became the first person in history to post a score of 59 (par was 72) in a PGA Tour-sanctioned event. He shot a bogey free round of six pars, eleven birdies, and one eagle. He went on to win the tournament.
In 1980, Geiberger had surgery to remove his colon due to inflammatory bowel disease and now has an ileostomy.
Geiberger's son Brent is also a professional golfer and has won two PGA Tour events. Another son, John, is the coach of the Pepperdine University golf team that won the 1997 NCAA Championship.