Gysbert Johannes Muller, more commonly known as Johann Muller (born 6 January 1980 in Mossel Bay, South Africa), is a South African former rugby union player.
Muller played as a lock for the Sharks (Currie Cup), Sharks in (Super Rugby) and his country's national side Springboks, before he moved to Northern Ireland to play with Ulster in 2010, where became team captain, before retiring at the end of the 2013–2014 season.