The Gai-As Formation is an Early to Middle Permian (Kungurian to Wordian) geologic formation correlated with the Ecca Group and designated "Ecca" Group, because it does not belong to the Karoo, in the southwestern Kunene Region and northern Erongo Region of northwestern Namibia. The Gai-As Formation represents the second-oldest sedimentary unit of the , overlying the Huab Formation. The formation was deposited in a fluvial to lacustrine setting.