Jiankang (Chinese: 建康城; pinyin: Jiànkāng chéng) was the capital city of the Eastern Jin Dynasty (317–420 CE) and Southern Dynasties. Its walls are extant ruins in the modern municipal region of Nanjing.

Before the Eastern Jin the city was known as Jianye (建業 Jiànyè), and the capital of the kingdom of Wu during the Three Kingdoms period. Renamed Jiankang in 313 CE, it served as the capital of the Eastern Jin and Southern Dynasties. It rivaled Luoyang in terms of population and commerce and at its height in the sixth century was home to around one million people. During the rebellion of Hou Jing, Jiankang was captured in 549 CE after a year-long siege that devastated the city, with most of the population killed or starved to death. During the Sui Dynasty national reunification it was almost completely destroyed, and was renamed Jiangzhou (蔣州) and then Danyang Jun (丹陽 郡). At the time of the Tang Dynasty it again became prosperous and the name became Jinling (金陵). By the Five Dynasties and Ten Kingdoms Period it was called Jiangning (江寧); in the Southern Song Dynasty the name of Jiankang was revived. Eventually it was renamed Nanjing (南京) during the Ming Dynasty.