Marnus is a masculine given name. Notable people with the name include:
Marnus Hugo (born 1986), South African rugby union player Marnus Labuschagne (born 1994), Australian cricketer Marnus Potgieter (born 1999), South African rugby union player Marnus Schoeman (born 1989), South African rugby union player Marnus van der Merwe (born 1997), South African rugby union player