Nodosaurus (no-doh-SORE-us) was a herbivorous dinosaur from the Late Cretaceous, the fossils of which are found in North America. Three incomplete specimens have been discovered in Wyoming and Kansas, and no skulls.

One of the first armored dinosaurs to be discovered in North America, Nodosaurus was named by Othniel Charles Marsh in 1889. This nodosaurid ankylosaur was about 13 to 20 feet (four to six metres) long. It was an ornithischian dinosaur with bony dermal plates covering the top of its body. It may have had spikes along its side as well. It had four short legs, five-toed feet, a short neck, and a long, stiff, clubless tail. The head was narrow, with a pointed snout, powerful jaws, and small teeth. It perhaps ate soft plants, as it would be unable to chew tough, fibrous ones; or alternatively it processed the latter by gastroliths and its enormous intestinal apparatus.

It is thought that without a club on its tail, Nodosaurus was left without much in terms of defense. When threatened, it probably dropped to the ground so that only its armored back and sides were exposed.