Loudon Snowden Wainwright III (born September 5, 1946) is an American songwriter, folk singer, humorist, and actor.

Wainwright's career began in the late 1960s. He had played the guitar while in school, but would later sell it for yoga lessons while living in San Francisco. Later, in Rhode Island, Wainwright's grandmother got him a job working in a boatyard. He was inspired by an old lobster fisherman named Edgar to borrow a friend's guitar and write his first song (entitled "Edgar"). Soon after, Wainwright bought a guitar and in about a year, he had written close to twenty songs. He decided to go to Boston and New York and began playing live shows in folk clubs. He was eventually "discovered" by Milton Kramer who became his manager. He acquired a record deal with Atlantic Records who released his first album in 1970.

Wainwright is known for the 1972 novelty song hit "Dead Skunk (in the Middle of the Road)" and for playing Captain Spalding (the "singing surgeon") on three episodes of the American television show M*A*S*H in its third season (1974-1975 including episode Rainbow Bridge), but his musical reputation is much deeper. Using a witty, self-mocking style, Wainwright has recorded over twenty albums on eleven different labels. Two of his albums have been nominated for Grammy awards.

Wainwright has also appeared in a number of films, including small parts in The Aviator, Big Fish, The 40 Year Old Virgin, Knocked Up and the television series Undeclared. Wainwright came to the attention of many people in Britain for the first time when he appeared as the resident singer with comedian Jasper Carrott in his UK show, Carrott Confidential, in the late 1980s, and he has remained popular in the UK ever since.

Wainwright has claimed that, like many of his contemporaries, he was inspired musically by seeing Bob Dylan at the Newport Folk Festival in 1962. He was one of many young folksingers tagged as the "new Dylan" in the early 1970s, a fact that he later ruefully satirized in his song "Talking New Bob Dylan" from 1992's History album.

In September of 2006, Wainwright and musician Joe Henry began composing the music to the Judd Apatow film, Knocked Up, which was released on June 1, 2007. In addition to composing the soundtrack, Wainwright appeared in the film in a supporting role as the protagonists' obstetrician.