Yanjing is a historical name for the ancient city of Ji, located in what is now the southwestern part of modern Beijing in northern China. The site is regarded as the longest continuously inhabited section of Beijing. Historical mention of Ji dates to the founding of the Zhou dynasty around 1045 BC, and archaeological finds in the area date to the Spring and Autumn period.
Ji served as the capital of the ancient states of Ji and Yan until China's unification under the Qin dynasty in 221 BC. It later functioned as a prefectural capital for Youzhou through the Han dynasty, the Three Kingdoms, the Western Jin, the Sixteen Kingdoms, the Northern Dynasties, and the Sui dynasty. During the Tang dynasty, with the creation of a separate Ji Prefecture in present-day Tianjin, the city became more exclusively known as Youzhou or by later names including Yanjing.
Youzhou was among the Sixteen Prefectures ceded to the Khitans during the Five Dynasties. The city subsequently became the southern capital of the Liao dynasty and then the main capital of the Jurchen Jin dynasty. In the 13th century, Kublai Khan built a new Yuan dynasty capital adjacent to Ji to the north; the old city became a suburb of Khanbaliq, or Dadu, whose site was developed under the Ming and Qing dynasties into modern Beijing.