Annam (ənăm´, ă´năm), historic region (c.58,000 sq mi/150,200 sq km) and former state, in central Vietnam, SE Asia. The capital was Hue. The region extended nearly 800 mi (1,290 km) along the South China Sea between Tonkin on the north and Cochin China on the south. In addition to Hue, the principal cities in the region are Da Nang (the chief seaport), An Nhon, Quang Tri, and Vinh. In 1954, when Vietnam was divided on a line approximating the 17th parallel, Annam went largely to South Vietnam. The ridge of the Annamese Cordillera separated N and central Annam from Laos on the west; the ridge then swung southeastward and ran along the coast of S Annam, which included the plateaus that stretched to the borders of Cambodia and Cochin China. The narrow coastal plains of N and central Annam were interrupted by spurs of mountains that almost reached the sea, as at Porte d'Annam, a pass important in Annamese history.
The origins of the Annamese state may be traced to the peoples of the Red River valley in N Vietnam. After more than 2,000 years of contact with the Chinese, they fell under Chinese rule as the result of a Han invasion in 111 BC The region, to which the Chinese gave the name Annam ( "Pacified South" ; a name resented by the people), comprised all of what later became N Annam and Tonkin. Southern Annam was occupied by the kingdom of the Chams, or Champa, from the late 2d cent. AD In 939 the Annamese drove out the Chinese and established their independence, which they maintained, except for one brief period of Chinese reoccupation (1407–28), until their conquest by the French in the 19th cent.
By 1558 the kingdom was in effect divided between two great families: the Trinh line, which ruled from Hanoi (then called Tonkin) as far south as Porte d'Annam (this area was called Tonkin by the Europeans who arrived in the 16th cent.), and the Nguyens, who ruled from Hue over the territory extending from Porte d'Annam south to the vicinity of Quy Nhon. The ruling dynasties of Hue and Tonkin were overthrown in 1778 and 1786 respectively, and the two domains were reunited (1802) as the empire of Vietnam by Nguyen-Anh, a Hue general, who had procured French military aid by ceding (1787) to the French the port of Da Nang and the Con Son islands. Nguyen-Anh established himself as emperor; his authority was formally recognized by the Chinese in 1803. In 1807 the Vietnamese extended a protectorate over Cambodia, which led in succeeding years to frequent wars against Siam.
After the death of Nguyen-Anh his successor, attempting to withdraw into isolation, mistreated French nationals and Vietnamese Christian converts. This provided an excuse for French military operations, which began in 1858 and resulted in the seizure of S Vietnam (Cochin China) and the establishment of protectorates (by 1884) over N Vietnam (Tonkin) and central Vietnam (Annam). The French, who abolished the name Vietnam, received recognition for their protectorates from the Chinese emperor. In 1887 Annam became part of the Union of Indochina. In World War II Indochina was occupied by the Japanese, who set up the autonomous state of Vietnam, comprising Tonkin, Annam, and Cochin China; Bao Dai, the last emperor of Vietnam, was established as ruler. After the war Annamese and Tonkinese nationalists demanded independence for the new state of Vietnam, and the region was plunged into a long and bloody conflict (see Vietnam).