Guyuan County (simplified Chinese: 沽源县; traditional Chinese: 沽源縣; pinyin: Gūyuán Xiàn) is a county under the administration of Zhangjiakou, Hebei, People's Republic of China.

It was once part of the province of Chahar, and now borders Inner Mongolia.

The area of the city is 2,621 square kilometres (1,012 sq mi), and the population as of 2020 is 167,587.

[1] Bordering county-level divisions are Fengning Manchu Autonomous County to the east, Chicheng County and Chongli District to the south, Zhangbei and Kangbao counties to the west, and, in Inner Mongolia, Taibus Banner, Zhenglan Banner and Duolun County to the north.

[2] It is a primarily mountainous county in northern Hebei, and thus has a cold climate with long, bitter winters and mild summers.