Stefanus Lourens Muller (1917–2005) was a South African politician and cabinet minister.

Muller worked for South African Railways before studying law and practicing as a lawyer in Robertson.

Muller initially worked under the Justice ministry, then held several ministerial posts under prime minister John Vorster with whom he had developed a close political alliance.

After Vorster's resignation as State President in the aftermath of the information scandal, Muller was widely considered the favourite to succeed him.

Muller was dismissed from the government by prime minister P. W. Botha, after a growing series of disagreements.