Teratosaurus was named by Meyer (1861). Its type is Teratosaurus suevicus. It is the type genus of Teratosauridae.

It was synonymized subjectively with Zanclodon by Lydekker (1888), Zittel (1890), Woodward and Sherborn (1890), Nopcsa (1901), Delair (1960).

It was assigned to Dinosauria by Huxley (1869), Cope (1870); to Zanclodontidae by Sauvage (1882), Marsh (1882), Vetter (1884), Dollo (1884), Marsh (1884), Marsh (1884), Marsh (1885), Huene (1902), Huene (1914); to Plateosauridae by Marsh (1895), Marsh (1896), Huene (1908), Huene (1909), von Zittel (1911), Huene (1914); to Carnosauria by Kuhn (1939); to Melanorosauridae by Romer (1966); to Carnosauria by Huene (1923), Huene (1926), Berckhemer (1938), Swinton (1970); to Ornithosuchidae by Walker (1964), Steel (1970); to Palaeosauridae by Kuhn (1971); to Megalosaurinidae by Huxley (1870), Welles (1984); to Teratosauridae by Cope (1871), Cope (1875), Nopcsa (1928), Romer (1956), Lapparent (1960), Tatarinov (1964), Charig (1967), Benedetto (1973), McIntosh (1981), Battail (1986); to Rauisuchia by Benton (1986); to Poposauridae by Galton (1985), Carroll (1988), Parrish (1993); to Rauisuchidae by Long and Murry (1995), Sulej (2005); to Paracrocodyliformes by Weinbaum and Hungerbühler (2007); and to Rauisuchidae by Brusatte et al. (2009).