Gary Ivan Mercer (born 22 June 1966) is a New Zealand rugby league and rugby union coach and former professional footballer. A New Zealand international representative player, he has spent most of his career in Britain both playing and coaching. He was a former defence coach of Glasgow Warriors and a former coach at the SRU working in their Scottish Rugby Academy.He is currently joint Head coach of Glasgow Hawks.
In his long career he has represented the New Zealand Kiwis within rugby league and New Zealand Māori sides and has played for the Leeds Rhinos, Bradford Northern, Warrington Wolves, Castleford Tigers and Halifax.
Gary Mercer played fullback in Bradford Northern's 12-12 draw with Castleford in the 1987 Yorkshire Cup final during the 1987–88 season at Headingley Stadium, Leeds on Saturday Saturday 17 October 1987, and played centre, i.e. number 4, in the 11-2 victory over Castleford in the 1987 Yorkshire Cup final replay during the 1987–88 season at Elland Road, Leeds on Saturday Saturday 31 October 1987.