The term 'The Fifth Beatle' is often used to refer to people who had a major influence on the success of the Beatles, but were not actually members of the band. Two of the most commonly cited people are George MARTIN and Yoko Ono. George MARTIN was a record producer who worked with the Beatles from 1962 until their break-up in 1970. He produced all of their albums and was an important mentor to the band. Yoko Ono was John Lennon's wife and a major influence on his music. She was also a vocal advocate for peace and social justice.