"I'm a Believer" is a song composed by Neil Diamond and recorded by the The Monkees in 1966 with the lead vocals by Micky Dolenz. The single, produced by Jeff Barry, hit the number one spot on the U.S. Billboard Hot 100 chart on December 31, 1966 and remained there for seven weeks, becoming the biggest-selling record for all of 1967, and one of the biggest of all time. Because of advance orders, over 1,051,280, it went gold within two days of release.

The song became Billboard's top single of the year and kept the novelty smash, "Snoopy Vs. The Red Baron" by The Royal Guardsmen, at number two for four weeks. Neil Diamond also suggested it to The Fifth Estate who recorded it as a 1967 album cut in follow up to their smash hit "Ding Dong! The Witch Is Dead". Neil Diamond had already recorded this song before it was covered by The Monkees, and it still sometimes appears in his live concerts. A revised recording by Neil Diamond, featuring additional lyrics, appears on the album September Morn, whilst his original recording can be found on several albums, including his greatest hits album, The Essential Neil Diamond.

A cover by British singer-songwriter Robert Wyatt was an unlikely hit in the UK in 1974. In 1995, British comedian Vic Reeves teamed up with then-popular band EMF for a version which reached #3 on the UK singles chart.

This song was also covered by Smash Mouth and Eddie Murphy in 2001, as part of the soundtrack to the movie Shrek(the band also released the song on its self-titled album). Eddie Murphy, portraying the character "Donkey", also performed a rendition of the song in the film. The song was chosen for its opening line, "I thought love was only true in fairy tales," which matched the fairy tale motif of the film. Subsequently, the song was played as exit music for the Broadway musical adaptation of the film, for comic effect. A year into the show's run, it was inserted into its finale. A nod to the version by Reeves & Mortimer with EMF is included in Shrek; though the "Oi!" does not appear in any album version of Smash Mouth's cover, it is inserted into the song when it is played in the film's finale, shouted by Snow White's Seven Dwarfs.

In 2008, this song ranked #1 on Dallas station KLUV 98.7FM's Top 500 Memorial Day Countdown, as voted on by the listeners. The song is listed at #48 on Billboard's All Time Top 100.[1]