Diarthrognathus ("Two joint jaw") was a genus of synapsid, known from fossil evidence found in South Africa. and first described in 1958 by A.W. Crompton. The creature lived during the Late Triassic to Early Jurassic periods, about 200 million years ago. It was carnivorous and small, slightly smaller than Thrinaxodon which was under 50 centimetres (20 in) long.