Korea (Korean: 한국, romanized: Hanguk in South Korea, or 조선, Chosŏn in North Korea) is a peninsular region in East Asia consisting of the Korean Peninsula (한반도, Hanbando in South Korea, or 조선반도, Chosŏnbando in North Korea), Jeju Island, and smaller islands. Since the end of World War II in 1945, it has been politically divided at or near the 38th parallel; in 1948, two states declared independence, both claiming sovereignty over the entire region: North Korea (Democratic People's Republic of Korea; DPRK) in its northern half and South Korea (Republic of Korea; ROK) in the south, which fought the Korean War from 1950 to 1953. The region is bordered by China to the north and Russia to the northeast, across the Amnok (Yalu) and Duman (Tumen) rivers, and is separated from Japan to the southeast by the Korea Strait.

Known human habitation of the Korean peninsula dates to 40,000 BC. The kingdom of Gojoseon, which according to tradition was founded in 2333 BC, fell to the Han dynasty in 108 BC. It was followed by the Three Kingdoms period, in which Korea was divided into Goguryeo, Baekje, and Silla. In 668 AD, Silla conquered Baekje and Goguryeo with the aid of the Tang dynasty, forming Unified Silla; Balhae succeeded Goguryeo in the north. In the late 9th century, Unified Silla collapsed into three states, beginning the Later Three Kingdoms period. In 918, Goguryeo was resurrected as Goryeo, which achieved what has been called a "true national unification" by Korean historians, as it unified both the Later Three Kingdoms and the ruling class of Balhae after its fall. Goryeo, whose name developed into the modern exonym "Korea", was highly cultured and saw the invention of the first metal movable type. During the 13th century, Goryeo became a vassal state of the Mongol Empire. Goryeo overthrew Mongol rule before falling to a coup led by General Yi Seong-gye, who established the Joseon dynasty in 1392.