Tonkin, also spelled Tongkin, Tonquin or Tongking, is an exonym referring to the northern region of Vietnam. During the 17th and 18th centuries, this term referred to the domain Đàng Ngoài under Trịnh lords' control, including both the Northern and Thanh-Nghệ regions, north of the Gianh River. From 1884 to early 1945, this term was used for the French protectorate of Tonkin, composed of only the Northern region.