Goguryeo, also known as Goryeo, was a Korean kingdom that existed from 37 BCE to 668 CE. Situated in the northern and central parts of the Korean Peninsula, it extended its influence into modern-day Northeast China, eastern Mongolia, Inner Mongolia, and parts of Russia. As one of the Three Kingdoms of Korea, along with Baekje and Silla, Goguryeo played a crucial role in the power dynamics of the Korean peninsula and had significant interactions with neighboring states in China and Japan. The Samguk sagi, a historical record from the 12th century, states that Goguryeo was founded in 37 BCE by Jumong, a prince from Buyeo. The name "Goryeo" was adopted as the official name in the 5th century and is the origin of the modern English term "Korea".

Goguryeo's early governance was characterized by a federation of five tribes, which evolved into districts with increasing centralization. By the 4th century, the kingdom had established a regional administration system centered around fortresses. As Goguryeo expanded, it developed the gun system, a form of county-based administration. The system further subdivided regions into seong (fortresses) or chon (villages), with a susa or other officials overseeing the county.

Militarily, Goguryeo was a force to be reckoned with in East Asia. The state had a highly organized army, capable of mobilizing up to 300,000 troops at its zenith. The military structure evolved over time, with reforms in the 4th century leading to significant territorial conquests. Every male citizen was required to serve in the military, with alternatives like paying additional grain tax. The kingdom's militaristic prowess was evident in its numerous tombs and artifacts, many of which had murals showcasing Goguryeo's warfare, ceremonies, and architecture.

Goguryeo's inhabitants had a vibrant lifestyle, with murals and artifacts depicting them in predecessors of the modern hanbok. They engaged in activities such as drinking, singing, dancing, and wrestling. The Dongmaeng Festival, held every October, was a significant event where rites were performed for ancestors and gods. Hunting was also a popular pastime, especially among males, serving both as entertainment and military training. Archery contests were common, highlighting the importance of this skill in Goguryeo society.

Religiously, Goguryeo was diverse. The people worshipped their ancestors and revered mythical beasts. Buddhism was introduced to Goguryeo in 372 and became an influential religion, with many monasteries and shrines built during the kingdom's reign. Shamanism was also an integral part of Goguryeo's culture. The cultural legacies of Goguryeo, including its art, dance, and architectural innovations like ondol (floor heating system), have persisted and can still be seen in modern Korean culture.