| Named By: | Othniel Charles Marsh in 1885 |
| Time Period: | Early Jurassic, 200-195 Ma |
| Location: | USA |
| Size: | Around 2 meters long, but if Ammosaurus is a synonym to Anchisaurus then possibly up to four meters long, though size would depend upon the specific species |
| Diet: | Herbivore |
| Fossil(s): | Few individuals |
| Classification: | | Chordata | Reptilia | Dinosauria | Saurischia | Sauropodomorpha | Anchisaura | Anchisauridae | |
| Also known as: | | Amphisaurus polyzelus | Megadactylus polyzelus | Yaleosaurus colurus | Ammosaurus | |
Anchisaurus is a type of early sauropodomorph dinosaur. It lived during the Early Jurassic Period, and its fossils have been found in the red sandstone of the Portland Formation, which was deposited from the Hettangian age into the Sinemurian age, between about 200 and 195 million years ago. Until recently it was classed as a member of Prosauropoda. The genus name Anchisaurus comes from the Greek agkhi/agkhi anchi-; "near, close" + Greek sauros/sauros; "lizard". 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.