The Korean Peninsula was inhabited from the Lower Paleolithic about 400,000-700,000 years ago. The earliest known Korean pottery dates to around 8000 BCE, and the Neolithic period began before 6000 BCE, followed by the Bronze Age by 800 BCE, and the Iron Age began around 400 BCE.

According to the mythic origin story recounted in the Samguk Yusa, the Gojoseon (Old Joseon) was founded in northern Korea and Manchuria in 2333 BCE. The Gija Joseon was founded in 12th century BC, and its existence and role have been controversial in the modern era. The Jin state was formed in southern Korea in the 3rd century BC. In the 2nd century BC, Gija Joseon was replaced by Wiman Joseon which fell to the Han dynasty of China near the end of the century. This resulted in the fall of Gojoseon and led to succeeding warring states, the Proto–Three Kingdoms period that spanned the later Iron Age. Since the 1st century, Goguryeo, Baekje, and Silla grew to control the peninsula and Manchuria as the Three Kingdoms (57 BC – 668 AD) until unification by Silla in 676. In 698, Dae Jo-yeong established the Kingdom of Balhae in old territories of Goguryeo, which led to the North South States Period (698–926).

Korea (/kəˈriːə/ kə-REE-ə; Korean: 한국 Hanguk [hanɡuːk] or 조선 Joseon [tɕosʌn] – (see etymology) is an East Asian region that is divided into two separate sovereign states — North Korea and South Korea. Located on the Korean Peninsula, Korea is bordered by China to the northwest, Russia to the northeast, and is separated from Japan to the east by the Korea Strait and the Sea of Japan (East Sea), and separated from Taiwan to the south by the East China Sea.

Archaeological and linguistic evidence suggest the origins of the Korean people might have been Altaic language-speaking people from south-central Siberia,^{[dubious – discuss]} who populated ancient Korea in successive waves from the Neolithic age to the Bronze Age. The adoption of the Chinese writing system ("Hanja" in Korean) in the 2nd century BC, and Buddhism in the 4th century AD, had profound effects on the Three Kingdoms of Korea.

The Three Kingdoms of Korea was first united during the Silla dynasty under the king Munmu of Silla. The united Silla dynasty fell to Goryeo Dynasty in 935 at the end of Later Three Kingdoms of Korea era. Goryeo was a highly cultural state and created the Jikji in the 14th century, using the world's first movable metal type printing press. The Mongol invasions in the 13th century, however, greatly weakened the nation which was forced to become a tributary state. After the Mongol Empire's collapse, severe political strife followed and Goryeo was replaced by the Joseon Dynasty in 1388.

The Korean War (Korean: 한국전쟁 or 조선전쟁, Hanja: 韓國戰爭 or 朝鮮戰爭; 25 June 1950 – 27 July 1953) was a war between the Republic of Korea (supported primarily by the United States of America, with contributions from allied nations under the aegis of the United Nations) and the Democratic People's Republic of Korea (supported by the People's Republic of China, with military and material aid from the Union of Soviet Socialist Republics). The Korean War was primarily the result of the political division of Korea by an agreement of the victorious Allies at the conclusion of the Pacific War at the end of World War II. The Korean Peninsula was ruled by the Empire of Japan from 1910 until the end of World War II. Following the surrender of the Empire of Japan in September 1945, American administrators divided the peninsula along the 38th parallel, with U.S. military forces occupying the southern half and Soviet military forces occupying the northern half.