David John Greenslade (born 18 January 1943) is an English composer and keyboard player. He has played with Colosseum from the beginning in 1968 until the farewell concert in 2015 and also from 1973 in his own band, Greenslade, and others including If and Chris Farlowe's Thunderbirds.

Greenslade was born in Woking, Surrey, England, the son of orchestral arranger Arthur Greenslade. Among his works are Cactus Choir, The Pentateuch of the Cosmogony (with art by Patrick Woodroffe) and From the Discworld. Television work includes music for the BBC series Gangsters (1975–1978), Bird of Prey (1982–1984) and A Very Peculiar Practice (1986).

After this he "virtually vanished from sight", becoming, as his friend Terry Pratchett proclaimed, "the man every TV producer in England would call when a new TV theme was needed". Greenslade's association with Pratchett, brought him back out into public view, with the 1994 release of From the Discworld, an album of music inspired by Pratchett's novels. Greenslade was active, between 1994 and 2015, after the re-forming of the band Colosseum.

Two more solo albums appeared, Going South and Routes/Roots, in 1999 and 2011 respectively.