Sanjuansaurus ("San Juan Province lizard") is a genus of herrerasaurid dinosaur from the Late Triassic (Carnian) Ischigualasto Formation of the Ischigualasto-Villa Unión Basin in northwestern Argentina.

The type species was named S. gordilloi after Raul Gordillo, the head fossil preparator and artist of the San Juan Museum.

Alcober and Martinez observed that Sanjuansaurus and Staurikosaurus share many similarities in the morphology of the hip bones, and the tibia.

[5] Studies suggest that the paleoenvironment of the Ischigualasto Formation was a volcanically active floodplain covered by forests and subject to strong seasonal rainfalls.

[8] Sanjuansaurus lived in the jungles of Late Triassic South America alongside early dinosaurs, Eoraptor, Herrerasaurus, Chromogisaurus, and Panphagia, as well as Saurosuchus,[9] a giant land-living rauisuchian (a quadrupedal meat eater with a theropod-like skull); the broadly similar but smaller Venaticosuchus, an ornithosuchid; and the predatory chiniquodontids.