Nipponosaurus, meaning “Japanese lizard”, is a genus of hadrosaurid dinosaur from the Late Cretaceous Period (late Santonian – early Campanian age). It was discovered in 1934 during the construction of a hospital on Karafuto Prefecture (now Sinegorsk, Sakhalin, Russia). More material belonging to this specimen was recovered in the summer of 1937. Though the quality of bone preservation is poor, the skeleton is about 60% complete. It is still one of the most poorly understood lambeosaurine dinosaurs.

Suzuki and colleagues re-described this dinosaur in 2004, and came to the conclusion that it was roughly 25 feet in length. It is considered a close relative to the well-known North American dinosaur Hypacrosaurus.