John Glascock was a British musician. He was the bassist and occasional lead vocalist of the rock band Carmen from 1972 to 1975; and the bass guitarist for progressive rock band Jethro Tull from 1976 until his death in 1979. Glascock died at the age of 28 as a result of a congenital heart valve defect, which was worsened by an infection caused by an abscessed tooth.

Carmen was an American-British band active from 1970 to 1975. Their style was a fusion of rock, progressive, and flamenco music and dance. Carmen's first album, Fandangos in Space, is ranked number 46 in the Rolling Stone list of 50 Greatest Prog Rock Albums of All Time.