Goguryeo (37 BC–668 AD) (; ko̞ɡuɾjʌ̹; : high castle; Old Korean: Guryeo) also later known as Goryeo (; ko.ɾjʌ; : high and beautiful; Middle Korean: 고ᇢ롕〮, Gowoyeliᴇ), was a Korean kingdom located in the northern and central parts of the Korean Peninsula and the southern and central parts of modern day Northeast China. At its peak of power, Goguryeo controlled most of the Korean Peninsula, large parts of Manchuria and parts of eastern Mongolia and Inner Mongolia as well as Russia.
Along with Baekje and Silla, Goguryeo was one of the Three Kingdoms of Korea. It was an active participant in the power struggle for control of the Korean peninsula and was also associated with the foreign affairs of neighboring polities in China and Japan.
The Samguk sagi (), a 12th-century text from Goryeo, indicates that Goguryeo was founded in 37 BC by Jumong (), a prince from Buyeo, who was enthroned as Dongmyeong.
Goguryeo was one of the great powers in East Asia, until its defeat by a Silla–Tang alliance in 668 after prolonged exhaustion and internal strife caused by the death of Yeon Gaesomun (). After its fall, its territory was divided between the Tang dynasty, Later Silla and Balhae.
The name Goryeo, alternatively spelled Koryŏ, a shortened form of Goguryeo (Koguryŏ), was adopted as the official name in the 5th century, and is the origin of the English name "Korea".
Goguryeo (; ko̞ɡuɾjʌ̹) is identified with the meaning of "high castle". Originally it was called Guryeo (Old Korean: 句麗 Kwulye (Yale; IPA: [ɡuɾ.jʌ̹]) or something similar to kaukuri [ko̞ːkɯ̟βɾji], both derived from 忽 *kuru or *kolo meaning castle, fortress, possibly a Wanderwort like the Middle Mongolian qoto-n.
Goguryeo was later shortened to the calque of Goryeo (; ko.ɾjʌ), which gained the meaning of "high and beautiful".
A number of possible cognates for 忽 exist as well, which was used at a later stage as a administrative subdivision with the spelling of hwol [hʌ̹ɭ], as in 買忽 mwoyhwol/michwuhwol [mit͡ɕhuhʌ̹ɭ], alongside the likely cognate of 骨 kwol [ko̞ɭ].