The Scunthorpe Mudstone is a geologic formation in England. It preserves plesiosaur fossils dating back to the Late Triassic (Rhaetian) to Early Jurassic (Hettangian) period. It predominantly consists of grey mudstone with thin beds of argillaceous limestone and calcareous siltstone. The Ichthyosaur Wahlisaurus is known from the formation. As is the holotype specimen of the dinosaur Sarcosaurus.