Cetiosaurus is a sauropod dinosaur whose remains were found in Oxfordshire. It was a herbivore.

Cetiosaurus was discovered in 1842. It was the first sauropod from which bones were described, and is the most complete sauropod found in England. The dinosaur was about 16 metres (52 ft) long and to have weighed roughly 11 tonnes (12 short tons). It is now known as Cetiosaurus oxoniensis.