Josias Johannes Nicolaas Swart (29 July 1934 - 18 January 1993), known as Sias Swart, was an international rugby union player for South Africa.

Born in Otjiwarongo, South West Africa, Swart was a descendant of Dorsland Trekkers and had six siblings.

Swart was the first Springbok to hail from South West Africa. He gained his sole Springboks cap playing on the left wing in the opening Test match against the 1955 British Lions at Ellis Park. His late try helped spark a Springboks comeback, but they were to lose by a single point, with Jack van der Schyff missing a shot at goal in the final moments.