Pterygotus is a genus of giant predatory eurypterid, an extinct group of aquatic arthropods. Fossils of Pterygotus have been discovered in deposits ranging in age from Late Silurian to Early Devonian, and have been referred to several different species. Fossils have been recovered from four continents; Australia, Europe, North America and South America, which indicates that Pterygotus might have had a nearly cosmopolitan distribution. The type species, P. anglicus, was described by Swiss naturalist Louis Agassiz in 1839. Agassiz mistakenly believed the remains were of a giant fish, with the name Pterygotus translating to "winged fish". He would only realize the mistake five years later in 1844.