Gaua (also known as Santa Maria Island) is the largest of the Banks Islands in Torba Province of northern Vanuatu. It covers 342 km².
It has rugged terrain, reaching up to Mount Gharat (797 m), the peak of the active stratovolcano at the center of the island. The most recent eruption was in 1982. The island was evacuated for four months in 1974 due to volcanic activity. The volcano has a 6 x 9 km caldera, within which lies a crater lake known as Lake Letas, the largest lake in Vanuatu. To the east of the lake is Siri Waterfall (120 m drop).
The island had a population of 780 in 1979, when the annual growth rate was estimated at a high 3.1 percent . This population is scattered in various coastal villages on the western, southern and northeastern sides of the island. The eastern side has a few hamlets with an immigrant population coming mainly from the two smaller islands Merig and Merelava, southeast of Gaua. Besides the language of this immigrant population (Mwerlap), there are five languages traditionally spoken on Gaua: Lakon or Vuré; Olrat; Koro; Dorig and Nume.
The population of Gaua lives of the traditional agricultural economy of Melanesia, combining fishing and horticulture. The principal exports are copra and cacao. Gaua has an airport (code ZGU).