Beichuan Qiang Autonomous County is a county under the jurisdiction of Mianyang City in northern Sichuan province, China. It is located in an ethnically diverse mountainous region of Sichuan. Its Chinese name literally means "North" (bei) "River" (chuan). Its new county seat is located at Yongchang after the 2008 Sichuan earthquake.

Mianyang is the second largest prefecture-level city of Sichuan province in Southwestern China. Located in north-central Sichuan covering an area of 20,281 square kilometres (7,831 sq mi) consisting of Jiangyou, a county-level city, five counties, and three urban districts. Its total population was 4,868,243 people at the 2020 Chinese census, of whom 2,232,865 live in its built-up area made of three urban districts.