Peter Michael McCartney BEM (born 7 January 1944), known professionally as Mike McGear, is an English musician and photographer who was a member of the groups the Scaffold and Grimms. He is the younger brother of former Beatle Paul McCartney.

Michael and his brother Paul were both born in the Walton Centre in Walton, Liverpool, England, where their mother, Mary McCartney, had previously worked as a nursing sister in charge of the maternity ward. Michael was not enrolled in a Catholic school because his father, Jim McCartney, believed that they leaned too much towards religion instead of education. At age 17, McCartney started his first job at Jackson's the Tailors in Ranelagh Street, Liverpool. The year after, he took an apprenticeship at Andre Bernard, a ladies' hairdresser in the same street.

At the time the Beatles became successful, Mike McCartney was working as an apprentice at a ladies’ hairdresser, where the staff included future actor Lewis Collins and budding comedian Jimmy Tarbuck. Simultaneously, he was a member of the Liverpool comedy-poetry-music group The Scaffold (along with Roger McGough and John Gorman). The group formed in 1962 (the year of the Beatles' first hit). Mike decided to use a stage name, so as not to appear to be riding his brother's coattails. After first dubbing himself "Mike Blank", he settled on "Mike McGear", "gear" being the Liverpudlian equivalent of "fab". The band was subsequently signed to Parlophone.

The Scaffold recorded a number of UK hit singles between 1966 and 1974, the most successful being the 1968 Christmas number one single, "Lily the Pink". McGear composed the band's next biggest hit, 1967's "Thank U Very Much". In 1968, he and McGough released a "duo" album (McGough & McGear) that included the usual Scaffold mix of lyrics, poems, and comedy. The Scaffold ended up hosting a TV programme, Score with the Scaffold, which limited the musical portion of their career, and they were dropped by Parlophone. McGear then signed to Island Records and released a solo musical album entitled Woman in 1972, which again included many tracks co-written with McGough, and The Scaffold subsequently released their own album on the label, Fresh Liver.

The Scaffold then added several other members and released two albums on Island in 1973 as GRIMMS (an acronym for Gorman-Roberts-Innes-McGear-McGough-Stanshall). However, McGear quit GRIMMS after the second album out of tension between himself and one of the poets added to the group.

McGear then signed to Warner Bros. Records and in 1974 released his second non-comedy musical album, McGear, in which he collaborated with his brother Paul and his band Wings. Although four singles were released from these sessions, only "Leave It" enjoyed any moderate chart success (No. 36 UK). However, also recorded during McCartney's sessions with Wings was a Scaffold "reunion" song, "Liverpool Lou", which became The Scaffold's last top-ten hit. This led to the group's re-formation in 1974, and they recorded and performed together through to 1977.

Individually, McGear released a few more singles. His final release, while still using the name Mike McGear, was the 1981 release "No Lar Di Dar (Is Lady Di)". This was a satirical tribute to Lady Diana Spencer, released at the time of her wedding to Prince Charles.

In the 1980s, after retiring from music, Mike McCartney decided to end his use of the "McGear" pseudonym and revert to using his family name.