Nyctosaurus (meaning "night lizard" or "bat lizard") is a genus of nyctosaurid pterosaur from the Late Cretaceous period of what is now the Niobrara Formation of the mid-western United States, which, during the time "Nyctosaurus" was alive, was covered in an extensive shallow sea. Some remains belonging to a possible "Nyctosaurus" species called "N.lamegoi" have been found in Brazil, making "Nyctosaurus" more diverse. The genus "Nyctosaurus" has had numerous species referred to it, though how many of these may actually be valid requires further study. At least one species possessed an extraordinarily large antler-like cranial crest.