Gansus is a genus of aquatic birds that lived during the Lower Cretaceous period, between 115 to 105 million years ago (mya). It was found in what is now Gansu province, western China. It is the oldest-known of the Ornithurae, the group which includes modern birds (Neornithes) and extinct related groups, such as "Confuciusornis", "Ichthyornis" and "Hesperornis".