Yanmen Commandery was an administrative subdivision (jùn) of the state of Zhao established c. 300 BC and of northern imperial Chinese dynasties until AD 758. It occupied lands in what is now Shanxi and Inner Mongolia. Its first seat was at Shanwu ; its later seats moved southeast to the more defensible sites at Yinguan and Guangwu.

Dai County, also known by its Chinese name Daixian, is a county in Xinzhou, Shanxi Province, China. Its county seat at Shangguan is also known as Daixian. The county has an area of 1,729 km2 (668 sq mi) and had a population of 178,870 at the time of the 2020 census. The county is the home of the AAAAA-rated Yanmen Pass Scenic Area along the Great Wall, as well as the Bianjing Drum Tower, the Ayuwang Pagoda, and the Zhao Gao Forest Park.