South Korea (officially the Republic of Korea), and commonly referred to as Korea, is a sovereign state in East Asia, constituting the southern part of the Korean Peninsula. The name Korea is derived from the Kingdom of Goryeo, also spelled as Koryŏ. It shares land borders with North Korea to the north, and oversea borders with Japan to the east and China to the west. Roughly half of the country's 50 million people reside in the metropolitan area surrounding its capital, the Seoul Capital Area, which is the second largest in the world with over 25 million residents.
Korea was inhabited as early as the Lower Paleolithic period and its civilization began with the founding of Gojoseon. After the unification of the Three Kingdoms of Korea in 668, Korea enjoyed over a millennium of relative tranquillity under dynasties lasting for centuries in which its trade, culture, literature, science and technology flourished. In 1910 it was annexed by the Japanese Empire, after whose surrender in 1945 Korea was divided into Soviet and U.S. zones of occupation, with the latter becoming the Republic of Korea in August 1948. Although the United Nations passed a resolution declaring the Republic to be the only lawful government of Korea, a communist regime was soon set up in the North that invaded the South in 1950, leading to the Korean War that ended in 1953 with an armistice, with peace and prosperity settling-in thereafter.