Regnosaurus, which translates to "Regni lizard," (The name Regni was a tribe that habited Sussex) is a herbivorous stegosaurian dinosaur that inhabited what is now England during the Early Cretaceous Period. It stands among the earliest stegosaurs to be uncovered. The remains of Regnosaurus, specifically a fragment of the right lower jaw, were unearthed near Cuckfield in Sussex and became part of the British Museum of Natural History's collection. The sole specimen attributed to Regnosaurus is it´s holotype, comprising a portion of the right mandible - the lower jaw. This segment encompasses roughly one-third of the dentary bone and a portion of the splenial bone, all discovered within the Tunbridge Wells Sand Formation. This specimen measures six inches in length and contains fifteen tooth sockets, with some replacement teeth visible.

To date, the original jawbone is the sole confirmed fossil evidence for Regnosaurus. Consequently, this genus is currently regarded as a nomen dubium. Unless additional fossils are found that encompass an identical jaw segment, it remains impossible to attribute any further fossil findings to this genus. Hence, even though isolated remains have been considered potential members of the genus, they cannot officially be classified as such, as their authenticity cannot be substantiated.