Ansi City, also known as Ansi Fortress, was a Goguryeo fortified city in present-day Liaoning province, China. The city was founded in early 4th century after Goguryeo conquered the area, and received its name from a Han dynasty prefecture of the same name. The ruins of the city are identified with a site at Yingchengzi (营城子), 7.5 kilometres (4.7 mi) to the southeast of Haicheng. Ansi was a major city of the Goguryeo and the scene of a major siege and battle between the Goguryeo and Tang dynasty China in 645 CE.