Vietnam (, ; Việt Nam ), officially the Socialist Republic of Vietnam (Cộng hòa xã hội chủ nghĩa Việt Nam), is the easternmost country on the Indochina Peninsula. With an estimated million inhabitants, it is the world's 15th-most-populous country, and the ninth-most-populous Asian country. Vietnam is bordered by China to the north, Laos to the northwest, Cambodia to the southwest, Thailand across the Gulf of Thailand to the southwest, and the Philippines, Malaysia and Indonesia across the South China Sea to the east and southeast. Its capital city has been Hanoi since the reunification of North and South Vietnam in 1976, with Ho Chi Minh City as the most populous city.
The northern part of Vietnam was part of Imperial China for over a millennium, from 111 BC to AD 939. An independent Vietnamese state was formed in 939, following a Vietnamese victory in the battle of Bạch Đằng River. Successive Vietnamese imperial dynasties flourished as the nation expanded geographically and politically into Southeast Asia, until the Indochina Peninsula was colonised by the French in the mid-19th century. Following a Japanese occupation in the 1940s, the Vietnamese fought French rule in the First Indochina War. On 2 September 1945, President Hồ Chí Minh declared Vietnam's independence from France under the new name of the Democratic Republic of Vietnam. In 1954, the Vietnamese declared victory in the battle of Điện Biên Phủ which took place between March and May 1954 and culminated in a major French defeat. Thereafter, Vietnam was divided politically into two rival states, North Vietnam (officially the Democratic Republic of Vietnam) and South Vietnam (officially the Republic of Vietnam). Conflict between the two sides intensified in what is known as the Vietnam War with heavy intervention by the United States on the side of South Vietnam from 1965 to 1973. The war ended with a North Vietnamese victory in 1975. Vietnam was then unified under a communist government but remained impoverished and politically isolated. In 1986, the Communist Party of Vietnam (CPV) initiated a series of economic and political reforms that began Vietnam's path toward integration into the world economy.
By 2010, it had established diplomatic relations with 178 countries. Since 2000, Vietnam's economic growth rate has been among the highest in the world, and in 2011, it had the highest Global Growth Generators Index among 11 major economies. Its successful economic reforms resulted in its joining the World Trade Organization (WTO) in 2007. Vietnam is a member of the Association of Southeast Asian Nations (ASEAN), Asia-Pacific Economic Cooperation (APEC) and the Organisation Internationale de la Francophonie (OIF).