Uiju Castle is a historic structure located on the Chinese border, along the Yalu River in Uiju County, in North Pyongan Province, North Korea. A structure first built during the Ri Dynasty was designed to serve as the main border town (Uiju) in the area and was one of the most important northern defense posts during this time (the area had been fortified since the time of the Koryo dynasty). The present castle was built in 1520, it probably included parts of the old fortress. It is listed as one of the National Treasures of North Korea.