The Fen River (Chinese: 汾河; pinyin: Fén Hé) drains the center of Shanxi Province, China. It rises in the Guancen Mountains of Ningwu County in northeast Shanxi, flows southeast into the basin of Taiyuan, and then south through the central valley of Shanxi before turning west to join the Yellow River west of Hejin. The Fen and the Wei Rivers are the two largest tributaries of the Yellow River. The river is 694 km long and drains an area of 39,417 km², 25.3% of the area of Shanxi Province. The Fen River is the longest river in Shanxi province, northern China. It is also the second longest tributary of the Yellow River.