Maiasaura is a large herbivorous hadrosaurid dinosaur genus that lived in the area currently covered by the state of Montana in the Upper Cretaceous Period (mid to late Campanian), about 76.7 million years ago.
The first fossils of Maiasaura were discovered in 1978. In 1979, the genus was named. The name refers to the find of nests with eggs, embryos and young animals, in a nesting colony. These showed that Maiasaura fed her young while they were in the nest, the first time such evidence was obtained for a dinosaur.