Matthew Grevers (born March 26, 1985) is a former American competition swimmer who competed in the backstroke and freestyle events, and is a six-time Olympic medalist. He has won a total of thirty-three medals in major international competition, fourteen gold, twelve silver, and seven bronze spanning the Olympics, World Championships, and the Universiade. At the 2008 Summer Olympics, Grevers won gold medals as a member of the U.S. teams in the 4×100-meter freestyle and 4×100-meter medley relays, and a silver medal in the 100-meter backstroke. Four years later, at the 2012 Summer Olympics, he won gold medals in the 100-meter backstroke and the 4×100-meter medley relay, and a silver medal in the 4×100-meter freestyle relay.

Born on March 26, 1985, in Lake Forest, Illinois, to Ed and Anja Grevers, a swim coach, he attended Lake Forest High School. One of the younger competitive swimmers in the family, older sister Carolyn swam for the University of Kansas, while older brother Andrew swam for Northern Illinois. Recognized early for his potential at High School meets, he set a national backstroke record at ten. At Lake Forest, he set three Illinois state records and in his Senior year in 2003 made significant contributions to Lake Forest's first Illinois State Team Championship. During his High School years, he competed and trained with Patriot Aquatics Swim Club at Illinois's Stevenson High School under accomplished coach Lea Maurer, a 1992 Olympic gold medalist who served as an Assistant Coach at Northwestern, and would later coach at Stanford. Completed in 1996, the club featured one of the first and most modern natatoriums in the state.

Beginning as a Freshman swimmer with Northwestern University in the fall of 2003, Grevers was a Big 10 Freshman of the Year, and became the first Northwestern Wildcat swimmer since 1958 to capture a national championship when he finished ahead of Ryan Lochte of Florida in the 100 backstroke at the 2005 NCAA championships. At Northwestern, he was a 27-time All American, and was trained and managed by Coach Bob Groseth. He won three individual NCAA titles during his time at Northwestern, and captured a fourth NCAA national championship with Northwestern's 400 medley relay team in 2007.

He repeated as the winner of the NCAA 100 backstroke title in 2006, then captured a first in the 200 backstroke, becoming only the third swimmer in the history of the NCAA history to swim under a time of 1:40 in the event.

A 2006 Big Ten Swimmer of the Year, he graduated Northwestern with three Big Ten Conference records, 11 Northwestern University records and 10 Norris Aquatics Center pool records.

At the 2008 Summer Olympics in Beijing, China, Grevers won two gold medals by swimming in the preliminary heats of the 4×100-meter freestyle relay and 4×100-meter medley relay (swimming the backstroke leg) as the Americans went on to win the finals in those events and medals are awarded to participants at any step along the way. Grevers also won an individual silver medal in the 100-meter backstroke in a time of 53.11-second, 0.57 of a second behind the winner, world record holder Aaron Peirsol.

At the 2009 World Aquatics Championships, Grevers was part of the U.S. men's 4×100-meter freestyle relay team who took the gold ahead of Russia and France. Grevers also earned a gold in the 4×100-meter medley relay for his contributions in the heats.

At the 2012 United States Olympic Trials, the qualifying meet for the 2012 Olympics, Grevers qualified for the U.S. Olympic team by finishing first in the 100-meter backstroke and third in the 100-meter freestyle. In the final of the 100-meter backstroke, Grevers recorded the fastest time in a textile suit and won in a time of 52.08 seconds, then the second-best effort of all time and just behind Aaron Peirsol's world record of 51.94. In the 100-meter freestyle, Grevers placed third with a time of 48.55, which ensured him a spot on the 4×100-meter freestyle relay. Grevers also competed in the 50-meter freestyle, and placed sixth in the final with a time of 22.09.