Anchisaurus is a genus of basal sauropodomorph, and was an early herbivorous dinosaur. It lived during the Early Jurassic Period; more specifically, the Pliensbachian to Toarcian ages, 200 to 188 million years ago. Until recently it was classed as a member of Prosauropoda. The name comes from the Greek αγχι/agkhi anchi-; "near, close" + Greek σαυρος/sauros; "lizard", probably referring to Marsh's interpretation of it as intermediate between primitive dinosaurs (at the time Palaeosaurus was an example of what was thought to be a primitive dinosaur) and more derived dinosaurs. Anchisaurus was coined as a replacement name for Amphisaurus, which was itself a replacement name for Hitchcock's Megadactylus, both of which had already been used for other animals.

Hitchcock collected these bones under the name Megadactylus in 1865. Unfortunately, the name was in use, and the famous paleontologist Othniel Charles Marsh renamed it Anchisaurus in 1885. Remains thought to belong to this genus were found in South Africa and China, adding to the theory that these land masses were at the time joined in one super-continent, Pangaea, but these assignments have been contentious (Gyposaurus). A recovery from Nova Scotia may also be an Anchisaurus but this is unconfirmed.