Pterygotus is a genus of giant predatory eurypterid, a group of extinct aquatic arthropods. Fossils of "Pterygotus" have been discovered in deposits ranging in age from Late Silurian to Late 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 (worldwide) 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.