Francois Jakobus 'Frans' Viljoen (born 22 October 1982) is a South African rugby union footballer who plays as a loose forward.
Viljoen represented the in the Currie Cup and the in Super Rugby. He has had something of a nomadic career with spells playing for the and in his home country and Aironi in Italy. He has also completed short loan spells for Stade Français and the .
Only 13 July 2013 it was announced that Viljoen would join French side Lyon.