"Blue Moon" is a classic popular song written by Richard Rodgers and Lorenz Hart in 1934. It may be the first instance of the familiar "50s progression" in a popular song and has become a standard ballad. The song was a hit twice in 1949, with successful recordings in the U.S. by Billy Eckstine and Mel Tormé.

In 1961, "Blue Moon" became an international number-one hit for the doo-wop group The Marcels, on the Billboard 100 chart and in the UK Singles chart. Over the years, "Blue Moon" has been covered by various artists, including versions by Frank Sinatra, Billie Holiday, Elvis Presley, Sam Cooke, The Platters, The Mavericks, Dean Martin, Yvonne De Carlo, The Supremes, Cyndi Lauper, Bob Dylan, the Beatles, Beck, and Rod Stewart. Bing Crosby included the song in a medley on his album On the Happy Side (1962). The Cowboy Junkies recorded the song on their album The Trinity Sessions.