South Korea, officially the Republic of Korea, is a country in East Asia, constituting the southern part of the Korean Peninsula and sharing a land border with North Korea. The name Korea is derived from Goguryeo, which was one of the great powers in East Asia during its time, ruling most of the Korean Peninsula, Manchuria, parts of the Russian Far East and Inner Mongolia under Gwanggaeto the Great.
The Korean Peninsula was inhabited as early as the Lower Paleolithic period. Its first kingdom was noted in Chinese records in the early 7th century BC. Following the unification of the Three Kingdoms of Korea into Silla and Balhae in the late 7th century, Korea was ruled by the Goryeo dynasty (918–1392) and the Joseon dynasty (1392–1897).
The succeeding Korean Empire was annexed into the Empire of Japan in 1910. After World War II, Korea was divided into Soviet and U.S.-administered zones, with the U.S administered zone (South Korea) becoming the Republic of Korea in August 1948. An invasion initiated by North Korea led to the Korean War (1950–1953). The Korean Armistice Agreement brought about a ceasefire, but no peace treaty was signed.