The Fifth Beatle can refer to one (or more) of several people who were at one point a member of The Beatles, or had a strong association with the "fab four", other than John Lennon, Paul McCartney, George Harrison, or Ringo Starr.

Before they were famous, The Beatles actually did have five members, so the fifth Beatle might best be described as their bassist at the time, Stuart Sutcliffe, who left the band and shortly thereafter died of a brain hemorrhage. Similarly, their drummer at the time, Pete Best (later replaced by Ringo) also fits the bill.

But perhaps the epithet most commonly refers to George Martin, who produced nearly all their recordings. Martin's extensive musical training and sophisicated guidance are often credited with substantial musical and inspirational contributions to the work of The Beatles; some contend that he is responsible for transforming a good rock and roll group into some of the best-regarded, most important and influential popular musicians of any era.

However, Billy Preston is regarded by some to have an equal claim to the title of the fifth Beatle. Preston was the only artist to receive joint credit on a Beatles record, by playing the electric piano on "Get Back". Preston also played the keyboard on "Let It Be". Preston had been introduced to the Beatles during the early 1960s, but did not see them until 1969, when Harrison invited him to join them for recording sessions in order to defuse tensions in the band. Lennon once suggested that Preston join the Beatles, but the idea was dismissed by the others, as by that time, they were on the verge of breaking up.

Other people who have been referred to as (or claimed to be) "the Fifth Beatle" include:

• Brian Epstein, the band's manager until his death in 1967
• Neil Aspinall, assistant, road manager and close personal friend of the four. The Beatles once claimed he was indeed the fifth member.
• Mal Evans, roadie, assistant, and friend.
• Murray the K, a disc-jockey who made the completely unfounded claim to be the Fifth Beatle.

• As a joke, Eddie Murphy starred in a Saturday Night Live sketch, playing the role of "Clarence", a man who claimed to be the fifth Beatle, as saxophonist, who was kicked out by John and Paul because they wanted to steal the glory. The sketch featured Clarence's "proof" of his claims: Some out-of-tune saxophone and backing vocal parts clumsily overdubbed on a few Beatles songs, and an obviously phony picture of Clarence standing in the middle of the four Beatles.
• Similarly, an episode of The Simpsons featuring Paul and Linda McCartney included a scene in which Apu Nahasapeemapetilon claimed to be the fifth Beatle. (Paul's weary response? "Sure you were, Apu.")
• An edition of BBC comedy Fist of Fun featured a 'special guest' (played by Kevin Eldon) who claimed to be the fifth Beatle. The fact that he was born in 1971 didn't appear to be problem to the man as he remarks, with some wonder 'If I had been born twenty years earlier, I could have been the fifth Beatle!'