Bolong yixianensis was a small basal hadrosauroid dinosaur that lived during the Early Cretaceous period about 125 million years ago in what is now Liaoning Province, China. Fossils were discovered in the Yixian Formation, a famous deposit known for exceptionally preserved dinosaurs and other prehistoric life. Bolong represents an early stage in the evolution of duck-billed dinosaurs, belonging to the lineage that would later produce the large hadrosaurids of the Late Cretaceous. The animal had a relatively small skull, a slender body, and long hind limbs, indicating it was likely a fast and agile herbivore.

Like other early ornithopods, Bolong probably moved primarily on two legs but could also adopt a quadrupedal stance while feeding. Its jaws contained numerous small teeth arranged for slicing plant material, allowing it to process vegetation efficiently. At roughly 3 meters in length, it was much smaller than later duck-billed dinosaurs but provides important insight into the early diversification of hadrosauroid herbivores during the Early Cretaceous ecosystems of northeastern Asia.