English rock bassist. Born 2 May 1951 in London, died 17 November 1979 in London. Brother of Brian Glascock.

John Glascock, Jethro Tull's third bass player, was the first member of Jethro Tull to have had a recording career that didn't start with Ian Anderson. He was with the band for only four years (1975-1979), before he died suddenly at the age of twenty eight from complications stemming from a congenital heart defect.