"Monday, Monday" is a 1966 song written by John Phillips and recorded by the Mamas & the Papas using background instruments played by members of The Wrecking Crew for their 1966 album If You Can Believe Your Eyes and Ears. It was the group's only number-one hit on the U.S. Billboard Hot 100.

Phillips said that he wrote the song quickly, in about 20 minutes. The song includes a false ending, when there is a pause before the coda of the song, and goes up a half note for the bridges and refrains of the song. It was the second consecutive number-one hit song in the U.S. to contain a false ending, succeeding "Good Lovin'" by the Young Rascals, and the first time this novelty had occurred between consecutive number one hits.

On March 2, 1967, The Mamas & the Papas won a Grammy Award for Best Pop Performance by a Duo or Group with Vocal for this song.

Arguably the best live or studio version of the song was performed at the Monterey Rock Festival (California) in 1967. The performance was recorded for film at the time but not in a solo album.

The song appears on the soundtrack of Michael Apted's film Stardust.

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