Ian Lowell Crocker (born August 31, 1982 in Portland, Maine) is an American swimmer who won gold medals in both the 2000 and 2004 Summer Olympics as a member of national team in the 4x100 medley relay. Both teams set world records in the event. He trains six days a week, up to 12 km of swimming per day and is based at the University of Texas at Austin, where he trains alongside fellow world record holders Aaron Peirsol and Brendan Hansen under Eddie Reese. He is an alumnus of Cheverus High School.
Crocker, who specializes in the butterfly, has received four Olympic medals in his career. At the 2000 Summer Olympics, Crocker was a member of the gold medal-winning 400 meter medley relay team and barely missed winning a bronze in the 100 meter butterfly. At the 2004 Summer Olympics, he received a bronze medal as a member of the 400 meter freestyle relay team, a silver medal in the 100 meter butterfly, and a gold medal as a member of the world-record setting 400 meter medley relay team (with a split of 50.28). Of the three medals he won at the 2004 Summer Olympics, he is best remembered for his silver, as teammate Michael Phelps overtook him at the very end of the 100 meter butterfly to win the race by .04 seconds. As a result, Phelps qualified for the 400 meter medley relay team. Phelps would eventually decide to give his spot on the relay team to Crocker, as Phelps was exhausted from the number of races that he entered in those Olympics, and wanted Crocker to win a gold medal himself.
In addition to his accomplishments at the Olympics, Crocker is the current world record holder in the 100 meter butterfly, with a time of 50.40 set at the 2005 World Aquatics Championships in Montreal. He is the first man to ever swim under 51 seconds in this event. Crocker, who has set several other world records in the 100 meter butterfly, won two golds and one silver at the 2003 World Aquatics Championships, and two golds and one silver at the 2005 World Aquatics Championships. Recently, Ian has said he is currently focusing on attempting to break 50 seconds in the 100 meter butterfly. At the 2007 World Aquatics Championships in Melbourne, Australia , Ian Crocker, who had been in position to derail Phelps in the 100 fly before losing to his rival, dove in too early on an exchange, causing the disqualification of the American team's 4x100 m medley relay.