"Sweet Sir Galahad" is a song written by Joan Baez that she performed at the Woodstock Festival in August 1969. She first performed it on Season 3, Episode 23, of The Smothers Brothers Comedy Hour earlier that year and included it on her album One Day at a Time (1970). The song tells the story of Baez' younger sister Mimi Fariña and her second marriage to music producer Milan Melvin. Mimi and Milan were married at the 1969 Big Sur Folk Festival. Baez was inspired to write the song, after hearing of Melvin's courtship of Fariña, during which he came into her bedroom at night through the window. It has since become one of Baez's best-known compositions.
In 2006, Baez contributed a "re-tooled" version of the song to Volume 1 of the XM Artist Confidential CD series, available at Starbucks. In the new version, Baez briefly changes the lyric "Here's to the dawn of their days" to "Here's to the dawn of her days," a tribute to the song's subject, Baez's sister Mimi, who had died in 2001. Milan Melvin, aka "Sir Galahad", also died in 2001.
A live version of the song appears as a bonus track on the 2006 reissue Baez' 1995 live album Ring Them Bells. It should not be confused with the Sir Galahad song by Rick Wakeman.