Dream Theater is an American progressive metal band formed in 1985 in Boston, Massachusetts. The band comprises John Petrucci (guitar), John Myung (bass), Mike Portnoy (drums), James LaBrie (vocals) and Jordan Rudess (keyboards).
Dream Theater was formed under the name Majesty by Petrucci, Myung and Portnoy—all natives of Long Island, New York—while they attended Berklee College of Music. They dropped out to concentrate on the band. Petrucci and Myung have been the only two constant members. Portnoy remained until 2010, when he was replaced by Mike Mangini after deciding to leave to pursue other musical projects, before rejoining Dream Theater in October 2023. After a brief stint with Chris Collins, followed by Charlie Dominici (who was dismissed from Dream Theater shortly after the release of their 1989 debut album When Dream and Day Unite), LaBrie was hired as the band's singer in 1991.