Goryeo (고려) was a Korean kingdom founded in 918, during a time of national division called the Later Three Kingdoms period, that unified and ruled the Korean Peninsula until 1392. Goryeo achieved what has been called a "true national unification" by Korean historians as it not only unified the Later Three Kingdoms but also incorporated much of the ruling class of the northern kingdom of Balhae, who had origins in Goguryeo of the earlier Three Kingdoms of Korea. The name 'Korea' is derived from the name of Goryeo, also spelled Koryŏ, which was first used in the early 5th century by Goguryeo. According to Korean historians, it was during the Goryeo period that the individual identities of Goguryeo, Baekje, and Silla were successfully merged into a single entity that became the basis of modern-day 'Korean' identity.

Goryeo - Wikipedia