South Korea, officially the Republic of Korea (ROK), is a country in East Asia. It constitutes the southern half of the Korean Peninsula and borders North Korea along the Korean Demilitarized Zone, with the Yellow Sea to the west and the Sea of Japan to the east. South Korea claims to be the sole legitimate government of the entire peninsula and adjacent islands. It has a population of about 52 million, of which half live in the Seoul metropolitan area, the ninth most populous metropolitan area in the world, with other major cities being Busan, Daegu, and Incheon.
The Korean Peninsula was inhabited as early as the Lower Paleolithic period. Its first kingdom was noted in Chinese records in the early seventh century BC. From the mid first century BC, various polities consolidated into the rival kingdoms of Goguryeo, Baekje, and Silla. The lattermost eventually unified most of the peninsula for the first time in the late seventh century AD, while Balhae succeeded Goguryeo in the north. The Goryeo dynasty (918–1392) achieved lasting unification and established the basis for the modern Korean identity. The subsequent Joseon dynasty (1392–1897) generated cultural, economic, and scientific achievements but maintained an isolationist policy from the mid-17th century. The succeeding Korean Empire (1897–1910) sought modernization and reform but was annexed in 1910 into the Empire of Japan. Japanese rule ended following Japan's surrender in World War II, after which Korea was divided into two zones: the Soviet-occupied northern zone and the United States-occupied southern zone.
After negotiations on reunification failed, the southern zone became the Republic of Korea in August 1948, while the northern zone became the Soviet-aligned Democratic People's Republic of Korea the following month. In 1950, a Soviet-backed North Korean invasion triggered the Korean War, one of the first major proxy conflicts of the Cold War, which saw extensive fighting involving the American-led United Nations Command and the People's Volunteer Army from China. The war ended in 1953 with an armistice and left three million Koreans dead and the economy in ruins; due to the lack of a peace treaty, the Korean conflict is still ongoing. South Korea endured a series of dictatorships punctuated by coups, revolutions, and violent uprisings, but also experienced a soaring economy and one of the fastest rises in average GDP per capita, leading to its emergence as one of the Four Asian Tigers. The June Democratic Struggle of 1987 ended authoritarian rule and led to the establishment of the current Sixth Republic.
South Korea is now considered among the most advanced democracies in Asia. Under the 1987 constitution, it maintains a unitary presidential republic with a popularly elected unicameral legislature, the National Assembly. South Korea is a major non-NATO ally of the United States and regarded as a regional power in East Asia and an emerging power in global affairs; its conscription-based armed forces are ranked as one of the strongest in the world and have the second highest number of military and paramilitary personnel. A highly developed country, South Korea's economy ranks the 14th largest in the world by nominal GDP and PPP-adjusted GDP; it is the world's ninth-largest exporter and tenth-largest importer. The country performs well in metrics of education, human development, democratic governance, and innovation. It has one of the world's longest life expectances, though its population is aging rapidly and has one of the lowest fertility rates in the world. South Korea has some of the fastest Internet connection speeds and densest high-speed railway networks. Since the turn of the 21st century, the country has been renowned for its globally influential pop culture, particularly in music, TV dramas, and cinema, a phenomenon referred to as the Korean Wave. South Korea is a member of the OECD's Development Assistance Committee, the G20, the IPEF, and the Paris Club.
The name Korea is an exonym derived from the historical Korean kingdom name Goryeo (Korean: 고려; Hanja: 高麗; MR: Koryŏ). Goryeo was the shortened name officially adopted by Goguryeo in the 5th century and the name of its 10th-century successor state Goryeo. Visiting Arab and Persian merchants pronounced its name as "Korea". The modern name of Korea appears in the first Portuguese maps of 1568 by João vaz Dourado as Conrai and later in the late 16th century and early 17th century as Corea (Korea) in the maps of Teixeira Albernaz of 1630.
The Kingdom of Goryeo became first known to Europeans when Afonso de Albuquerque conquered Malacca in 1511 and described the people who traded in this part of the world as the Gores. Despite the coexistence of the spellings Corea and Korea in 19th-century publications, some Koreans believe that Imperial Japan intentionally standardized the spelling of Korea in order to make Japan appear first alphabetically during occupation.
After Goryeo was replaced by the Kingdom of Joseon (조선; 朝鮮; Chosŏn) in 1392, Joseon became the official name for the entire territory, though it was not universally accepted. The new official name was derived from the ancient kingdom of Gojoseon. In 1897, King Gojong changed the country's official name from Joseon to the Korean Empire (대한제국; 大韓帝國; Daehan Jeguk; Taehan Cheguk; lit. 'Great Han Empire'). The latter half of the Korean Empire's name Daehan (대한; 大韓; lit. 'Great Han') derives from Samhan (Three Han), referring to the Three Kingdoms of Korea, not the ancient confederacies in the southern Korean Peninsula. However, the name Joseon was still widely used by Koreans to refer to their country, even though it was no longer the official name. Under Japanese rule, the two names Han and Joseon coexisted.
Following the surrender of Japan, in 1945, the "Republic of Korea" was adopted as the legal English name for the new country. The Korean name Daehan Minguk (대한민국; 大韓民國; lit. 'Great Han Republic') is sometimes used by South Koreans as a metonym to refer to the Korean nation as a whole, rather than just the South Korean state.
The Korean Peninsula was inhabited as early as the Lower Paleolithic period. According to Korea's founding mythology, the history of Korea begins with the founding of Joseon (also known as "Gojoseon", or "Old Joseon", to differentiate it from the 14th century dynasty) in 2333 BC by the legendary Dangun. Gojoseon was noted in Chinese records in the early 7th century. Gojoseon expanded until it controlled the northern Korean Peninsula and parts of Manchuria. Gija Joseon was purportedly founded in the 12th century BC, but its existence and role have been controversial in the modern era. In 108 BC, the Han dynasty defeated Wiman Joseon and installed four commanderies in the northern Korean peninsula. Three of the commanderies fell or retreated westward within a few decades, but the Lelang commandery remained a center of cultural and economic exchange with successive Chinese dynasties ruling for four centuries, until it was conquered by Goguryeo in 313.
The linguistic homeland of Proto-Koreans is located somewhere in southern Siberia, or Manchuria, such as the Liao River area or the Amur River area. Proto-Koreans arrived in the southern part of the Korean Peninsula at around 300 BC, replacing and assimilating Japonic-speaking Yayoi and likely causing their migration to the Japanese archipelago.
During the Proto–Three Kingdoms period, the states of Buyeo, Okjeo, Dongye, and Samhan occupied the whole Korean peninsula and southern Manchuria. From them, the Three Kingdoms of Korea emerged: Goguryeo, Baekje, and Silla.
Goguryeo, the largest and most powerful among them, was a highly militaristic state and competed with various Chinese dynasties during its 700 years of history. Goguryeo experienced a golden age under Gwanggaeto the Great and his son Jangsu, who both subdued Baekje and Silla during their respective reigns, achieving a brief unification of the Three Kingdoms and becoming the most dominant power on the Korean Peninsula. In addition to contesting control of the Korean Peninsula, Goguryeo had many military conflicts with various Chinese dynasties, most notably the Goguryeo–Sui War, in which Goguryeo defeated a huge force said to number over a million men.