Aaron Wells Peirsol (born July 23, 1983) is an American former competition swimmer and backstroke specialist who is a former world champion and world record-holder. He is a three-time Olympian and seven-time Olympic medalist (five gold, two silver). As a member of the U.S. national team, he holds the world record in the men's 4×100-meter medley relay (long course). Individually, he currently holds the world record in the 200-meter backstroke event (long course). In February 2011, Peirsol announced his retirement, saying, "I ended up doing everything I set out to do."
Peirsol's successes have earned him the American Swimmer of the Year Award once. He has won a total of thirty-six medals in major international competition, twenty-nine gold, six silver, and one bronze spanning the Olympics, the World, Pan American, and the Pan Pacific Championships.
In his Olympic debut at the 2000 Summer Olympics, at the age of 17, Peirsol won a silver medal in the 200-meter backstroke. Four years later, at the 2004 Summer Olympics, Peirsol won gold in the 100-meter and 200-meter backstroke (sweeping the backstroke events) and the 4×100-meter medley relay. In his third Olympics (2008 Summer Olympics), Peirsol won gold in the 100-meter backstroke and the 4×100-meter medley relay. He came short of his success he had in Athens by winning silver in the 200-meter backstroke, finishing behind Ryan Lochte.
Peirsol was born in Newport Beach, California, in 1983, the son of Scott and Wella Peirsol. His father is a captain and his mother is a retired dental hygienist. He has one younger sister, Hayley, who is also a swimmer. Peirsol and his sister are the only sibling duo to medal at the same FINA World Championships (in 2003). He is a 2002 graduate of Newport Harbor High School in Newport Beach, California. Peirsol attended the University of Texas at Austin and graduated in 2006, majoring in Political Science. He was the 2003 NCAA Swimmer of the Year. After finishing his second year of collegiate eligibility, Peirsol signed with Nike, Inc., thus turning professional. Peirsol trained under the guidance of Eddie Reese and Kris Kubik.