Hengnan County (Chinese: 衡南县; pinyin: Héngnán Xiàn; lit.

'south of Mount Heng') is a county located in the south of Hengyang prefecture-level city, Hunan province, China.

The Ouyanghai Reservoir on the Chongling River irrigates thousands of hectares of arable land in the east.

As of 2013, the county had identified more than 30 metal and non-metallic minerals, mainly tungsten, copper-manganese, iron, uranium, aluminum gold, fluorite, barite, salt, coal, etc., in which barite With barium sulfate up to 94.8%.

The county has a subtropical monsoon humid climate with a sufficient heat, concentrated rainwater, cold winter and hot summer, distinct four seasons, variable spring temperatures, short freezing period, and long hot summer period.