Michael Josias du Plessis (born 4 November 1958) is a former South African rugby union player.
Du Plessis played for Western Province, Northern Transvaal, Transvaal, Eastern Province and the Springboks. He made his test debut against the visiting South American Jaguars team on 20 October 1984. Capped 8 times, he scored 1 try for the Springboks.
Du Plessis is the brother of Willie du Plessis and Carel du Plessis, both former Springboks, and the father of Daniël du Plessis.