The Big Three were a Merseybeat musical group from Liverpool, England. They are best known for their 1963 recording of "Some Other Guy", their live EP The Big Three at the Cavern from the same year, and for being direct contemporaries of the Beatles.

The Big Three evolved from a group called Cass and the Cassanovas, formed in May 1959 by Brian Cassar as a trio comprising Cassar (rhythm guitar, lead vocals), Adrian Barber (lead guitar, vocals), and Brian J. Hudson (drums). The original line-up played at St George's Hall, Liverpool, on Friday, 15 May 1959. Johnny Hutchinson replaced Hudson in July 1959. In need of a bass guitarist, Hutchinson brought in Johnny Gustafson in December. At that time, Gustafson did not have a proper bass guitar, so Barber converted an acoustic for him. Gustafson's first gig was at The Tower Ballroom, New Brighton, on 31 December 1959.

In May 1960, the band auditioned for Larry Parnes at the Wyvern Social Club, Seel Street, Liverpool, with a number of other bands including The Silver Beetles (one of The Beatles' earlier names). Hutchinson sat in with the Silver Beetles when their drummer Tommy Moore failed to turn up. In December 1960, Cassar left the group and moved to London, reducing them to a trio again, and the band re-emerged in January 1961 as The Big Three. Despite being a three-piece they were known as "one of the loudest, most aggressive and visually appealing acts".

Brian Epstein signed them to his agency and sent them over to Hamburg's Star-Club. During that trip in July 1962 Brian Griffiths joined the group, and the best-known line-up of the Big Three - Griffiths, Gustafson and Hutchinson - was established. Barber later emigrated to the United States, where he became known as an in-house recording engineer and producer at Atlantic Records, where he produced the Allman Brothers Band's debut album in 1969.

Epstein arranged for them to audition for Decca Records, for which they recorded "Some Other Guy", a standard in the Merseybeat scene, which became a minor chart hit.

The Big Three and Epstein terminated their partnership in July 1963. Gustafson and Griffiths quit in November 1963, and with drummer Ian Broad from Rory Storm and the Hurricanes formed the Seniors and left for Germany. Hutchinson replaced them with Faron Ruffley and Paddy Chambers from Faron's Flamingos. Gustafson would go on to be a member of The Merseybeats, Quatermass, Roxy Music and The Ian Gillan Band.

Chambers left in March 1964 and was replaced by Paul Pilnick from Lee Curtis' Allstars. Pilnick only stayed a short time before moving on to Tony Jackson & The Vibrations in October 1964, with Ruffley leaving around the same time.^{[citation needed]}

Various musicians passed through the band after Pilnick left, including bass players John Bradley, Adrian Lord (ex-Mojos), and Mike Bankes, while Ray Marshall and Howie Casey played saxophone on a trip to Germany. Barry Womersley was guitarist for a while, but was replaced by a returning Brian Griffiths during the time that they were managed by Chris Wharton. Wharton had hopes of re-enlisting Johnny Gustafson, but this came to nothing. Hutchinson had played with the Spidermen, but re-formed the group with Barry Womersley and Ray Marshall.^{[citation needed]}