"Pancho and Lefty" is a song written by country music artist Townes Van Zandt. Often considered his "most enduring and well-known song," Van Zandt first recorded it for his 1972 album The Late Great Townes Van Zandt. The song has been recorded by several artists since its composition and performance by Van Zandt, with the Willie Nelson and Merle Haggard version selling the most copies and reaching the Billboard top hits list.

A music video was released for the song in 1983, depicting Willie Nelson as Pancho, and Merle Haggard as Lefty. Townes Van Zandt also appears in a supporting role. Willie's daughter Lana (who incidentally was the one that suggested the recording of the duet) directed the video, the first for Nelson and second for Haggard, the first being for "Are the Good Times Really Over?"
The song reached No. 1 on Billboard's Hot Country Songs for chart dated July 23, 1983. In the Willie Nelson release, it has sold 648,000 digital copies in the United States as of October 2019 since becoming available for download.

The song has been covered by various artists, notably Merle Haggard and Willie Nelson's title track of their duet album Pancho & Lefty. This was a number one country hit and the Grammy Hall of Fame award in 2020.

Members of the Western Writers of America chose it as the 17th greatest Western song of all time.
In June 2004, Rolling Stone ranked "Pancho and Lefty" #41 on its list of the 100 Greatest Country Songs of All Time.