Yanshan (铅山) is a county in Shangrao Municipality, in north-eastern Jiangxi province.
It borders Hengfeng County to the north, Shangrao County to the east, Wannian County and Guixi City (in Yingtan) to the west and Wuyishan City and Guangze County (both in Nanping, FJ) to the south.
Hekou town sits on the Xinjiang River (信江), a tributary to Boyang Lake in the lower Yangzi River watershed.
The county seat, by Chinese convention often also called Yanshan, is at Hekou town (河口镇).
Coordinates: 28°19′05″N 117°42′14″E / 28.3181°N 117.704°E