Marthinus Coenraad Janse van Rensburg (29 December 1944 – 16 April 2017) was a South African international rugby union player.
Born in Ladysmith, van Rensburg was educated at Durban's Port Natal School.
A giant lock forward, van Rensburg represented Natal from 1965 and was a member of the Springboks squad on their 1969–70 tour of Britain and Ireland, where he played only minor fixtures. His tour was disrupted by a neck injury suffered against Swansea, for which he was carried off on a stretcher.