The Fen River 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. The Fen River in Taiyuan city is throughout from north to south, the length of Fen River in Taiyuan City is 100 kilometer, occupies one seventh of the entire Fen River.