Rayososaurus is a genus of plant-eating sauropod dinosaur of the superfamily Diplodocoidea. It was found in the Rayoso Formation, in Patagonia, Argentina and lived about 99 million years ago (during the Early Cretaceous). The type species is R. agrionensis, named by Argentinian paleontologist Jose Bonaparte in 1996.
There is some debate whether Rayososaurus is indeed a separate genus. However, morphological and temporal differences tend to support its claim. Fossil finds are only a scapula, femur and part of fibula. The racket-shaped scapula is characteristic of the Rebacchisauridae.