"Leaving on a Jet Plane" is a song written by John Denver in 1966 and most famously recorded by Peter, Paul and Mary. The original title of the song was "Babe, I Hate to Go", as featured on his 1966 studio album John Denver Sings, but Denver's then producer Milt Okun convinced him to change the title. Peter, Paul and Mary recorded the song for their 1967 Album 1700 but only released it as a single in 1969.

It turned out to be Peter, Paul and Mary's biggest (and final) hit, becoming their only No. 1 on the Billboard Hot 100 chart in the United States. The song also spent three weeks atop the easy listening chart and was used in commercials for United Airlines in the late 1970s. The song also topped the charts in Canada, and reached No. 2 in both the UK Singles Chart and Irish Singles Chart in February 1970.

In 1969, John Denver recorded a version of the song for his debut solo album, Rhymes & Reasons, and re-recorded it in 1973 for John Denver's Greatest Hits. His version was featured in the end credits of The Guard.

In the 1980s the song prompted litigation involving the British group New Order. The band's single "Run 2" (1989) was the subject of a lawsuit brought by John Denver, who argued that its wordless guitar break was based on his "Leaving on a Jet Plane". An out-of-court settlement ensured that the song would never be re-released in its original form.

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