Newtonsaurus is an extinct genus of possibly coelophysoid theropod dinosaur from the Late Triassic (Rhaetian) Lilstock Formation of South Wales, Great Britain. The genus contains a single species, Newtonsaurus cambrensis, originally named as a species of Zanclodon, known from an external mould of the front half of a lower jaw. With an estimated total length of 5–7 metres (16–23 ft), it is suggested to have been one of the largest theropods known from the Triassic.