Valdosaurus is a genus of dinosaur belonging to the family Dryosauridea. It lived approximately 100 million years ago during the Early Cretaceous period in what is now Europe, specifically in regions known as the Wessex Formation in the United Kingdom. The first fossils of Valdosaurus were discovered in the 19th century.

Valdosaurus was a small to medium-sized dinosaur, estimated to be around 5 meters in length. As an ornithopod, it belonged to a group of herbivorous dinosaurs known for their bipedal stance and herbivorous diet. Its slender body, long tail, and agile limbs suggest it was a fast and agile runner.

While specific details about its cranial anatomy remain limited, it is believed that Valdosaurus possessed a beak-like mouth and rows of cheek teeth ideally suited for grinding vegetation. However, the precise arrangement of its teeth and other cranial features are still under investigation. In 2016, a new specimen of Valdosaurus was discovered, representing the most complete finding to date. The specimen was found in articulation and includes a partial dorsal series, an almost complete tail, pelvic material, and both hind limbs. In life, this specimen would have measured around 4 to 5 meters (13 to 16 ft) in length.