Calamosaurus (meaning "reed lizard") was a genus of small theropod dinosaur from the Barremian-age Lower Cretaceous Wessex Formation of the Isle of Wight, England.

Richard Lydekker came across these bones when cataloguing the Fox collection and named them Calamospondylus foxi, noting their similarity to those of Coelurus.

A neck vertebra of a Calamosaurus was found near Chilton Chine on the Isle of Wight by local fossil hunter Dave Badman.

[20] Naish et al. (2001) tentatively referred the tibia to Calamosaurus foxi,[21] and NHMUK R.186 has since been moved to Calamospondylus oweni.

Naish et al. (2001) estimate the living animal would have been around 3–5 meters (9.8–16.4 ft) long, with a small head given the build of the neck vertebrae.