R.E.M. had four original members: Bill Berry, Peter Buck, Mike Mills, and Michael Stipe.
The band formed in Athens, Georgia, in 1980. Guitarist Peter Buck met vocalist Michael Stipe at the Wuxtry record store, and the two soon connected with drummer Bill Berry and bassist Mike Mills. Berry and Mills had already played together in bands while growing up in Macon, Georgia, which helped give the new group a ready-made rhythm section.
The quartet developed its sound through rehearsals in Athens and played its first show on April 5, 1980. Stipe chose the name R.E.M. at random from a dictionary; although the initials also refer to rapid eye movement, the band did not originally build its identity around that meaning.
R.E.M. remained a four-piece for most of its most influential period. Berry left in 1997 after suffering a brain aneurysm, but Buck, Mills, and Stipe continued as a trio with touring musicians. The band eventually broke up amicably in 2011. Berry's departure does not change the number of original members: the founding lineup was always four.