Mary Lou Retton (born January 24, 1968 in Fairmont, West Virginia) is an American gymnast. She was the first female gymnast outside Eastern Europe to win the Olympic all-around title.

Inspired by watching Nadia Comaneci on television, Retton took up gymnastics in her hometown of Fairmont, West Virginia. In 1982, she moved to Houston, Texas to train under the Romanians Bela and Martha Karolyi, who had coached Nadia Comaneci before their defection to the United States. Under the Karolyis, Retton soon began to make a name for herself in in the United States, winning the American Cup in 1983 and placing second to Dianne Durham (another Karolyi student) in the US Nationals in the same year. Retton, however, missed the World Championships in 1983 due to a wrist injury. Nevertheless, Retton managed to win the American Classic in 1983 and 1984, as well as Japan's prestigious Chunichi Cup in 1983.

After winning her second American Cup and the US Nationals and US Olympic Trials in 1984, Retton suffered a knee injury that forced her to undergo an operation. However, she recovered just in time for the 1984 Summer Olympics in Los Angeles. In the competition - which was boycotted by most of the Soviet bloc nations except for Romania - Retton engaged in a close battle with Ecaterina Szabo of Romania for the all-around title, to the delight of the patriotic audience. Trailing Szabó (after bars and beam) with two events to go, Retton scored perfect 10s on floor exercise and vault to win the all-around title by just 0.050.

At the same Olympics, Retton won four additional medals: a silver in the team competition and the horse vault, and bronze in the floor exercise and uneven bars. For her performance, she was named Sports Illustrated magazine's "Sportswoman of the Year". She is perhaps the most famous face to have appeared on a Wheaties box, and also the first woman to have done so. Her small stature led a wag at Sport magazine to comment that "Her life-size picture now appears on the Wheaties box."

During the 80s at the height of her popularity she was an outspoken supporter of the Reagan Administration in the United States. She appeared in a variety of televised ads supporting Ronald Reagan. Though still an outspoken Christian and conservative, she has since denounced Reagan and his years in office stating that had she "known the impact his inability to address the AIDS epidemic she would "never have given him (her) support." Retton did however deliver the Pledge of Allegiance with fellow former gymnast and 1996 Olympic Gold Medalist Kerri Strug on the fourth night of the 2004 Republican National Convention, and signed a letter expressing support from various U.S. athletes for the re-election of President George W. Bush.

The people in Retton's hometown of Fairmont, West Virginia were supportive of her Olympic endeavors. A street and park in Fairmont were later named after her. However, Retton rarely mentions her hometown and has made few visits there; she tells people that Texas is her home.

Retton retired from gymnastics after winning an unprecedented third American Cup title in 1985. She is currently married with four daughters and is a frequent analyst for televised gymnastics.

During the 1990s, she worked as a spokeswoman for the eastern U.S. drugstore chain Revco. In 1997 she was inducted into the International Gymnastics Hall of Fame.

Retton has a skill named after her on the uneven bars called, "The Retton Flip," a transition (front flip) from low to high-bar, resulting in the gymnast perched or "sitting" on top of the high bar.

As of 2006, Retton is currently the host of the children's program Mary Lou's Flip Flop Shop.