Xiyang County (simplified Chinese: 昔阳县; traditional Chinese: 昔陽縣; pinyin: Xīyáng Xiàn) is a county in the east of Shanxi province, China, bordering Hebei province to the east. It is the easternmost county-level division of the prefecture-level city of Jinzhong. Xiyang County is located at the western foot of Taihang Mountain, bordering Zanhuang County, Neiqiu County, Jingxing County, and Xingtai in Hebei province to the east, Heshun County to the south, and Pingding County in Yangquan to the north.

Xiyang County has five towns, five townships, and one urban social affairs service center under its jurisdiction.