Zephyrosaurus, whose name means "westward wind lizard," is an orodromine ornithischian dinosaur genus. The fossils used to describe it consist of a partial skull and postcranial fragments found in the Cloverly Formation, dating back to the Aptian-Albian-age Lower Cretaceous in Carbon County, Montana, USA. Additional remains are currently being studied, and tracks discovered in Maryland and Virginia in the United States have been linked to creatures resembling Zephyrosaurus. This dinosaur is estimated to have lived around 113 million years ago.

Zephyrosaurus remains largely a mystery due to the lack of complete information. Notably, it displayed several unique features, including a steep facial structure, an elevated knob on the upper jaw, and a larger knob on the cheekbone. Additionally, some of its cranial bones suggested potential movement within the skull (cranial kinesis). Like other orodromines, Zephyrosaurus possessed beak-like teeth.

Zephyrosaurus is believed to share a close relationship with Orodromeus and potentially Oryctodromeus due to the similar boss-like structures on its cheeks. Like these dinosaurs, Zephyrosaurus has been hypothesized to have been a burrowing creature, creating underground hideaways to evade predators like Deinonychus.

This relatively small ornithopod dinosaur likely fed on low-growing vegetation. When foraging, Zephyrosaurus would have depended on its speed and agility to avoid becoming prey for other predators.