Sonorasaurus is a genus of brachiosaurid dinosaur from the middle Cretaceous (Albian to Cenomanian stages, around 112 to 93 million years ago). It was a herbivorous sauropod whose fossils have been found in southern Arizona in the United States. Its name, which means "Sonora lizard", comes from the Sonoran Desert where its fossils were first found. It is estimated to have been about 15 meters long (50 ft) and 8.2 meters tall (27 ft), about one third of the size of Brachiosaurus.
Fossilized remains were discovered by geology student Richard Thompson, in 1995, in the Chihuahua Desert region of the Sonoran Desert in southern Arizona. Dating of the find makes this the first known brachiosaur to have lived in the middle Cretaceous Period of North America. The type species is S. thompsoni, described by Ratkevich in 1998.