Hydrosaurus, commonly known as the sailfin dragons or sailfin lizards, is a genus in the family Agamidae. These relatively large lizards are named after the sail-like structure on their tails. They are native to Indonesia and the Philippines where they are generally found near water, such as rivers and mangrove. Sailfin lizards are semiaquatic and able to run short distances across water using both their feet and tail for support, similar to the basilisks. They are threatened by both habitat loss and overcollection for the wild animal trade.

Agamidae is a family of over 550 species of iguanian lizards indigenous to Africa, Asia, Australia, and a few in Southern Europe. Many species are commonly called dragons or dragon lizards.