The Fensch (French pronunciation: [fɛnʃ]) or Fentsch is a river in the Moselle department of the Grand Est region of France.

It then crosses Knutange, Nilvange, Hayange, Serémange-Erzange and Florange before discharging from the left into the Moselle between Metz and Thionville on the border of the commune of Illange.

The springs of Morlange (now part of Fameck) and of Ranguevaux were captured in 1886 and carried by gravity to Thionville by a 10 kilometres (6.2 mi) long conduit.

High water events occur in winter and are characterized by average monthly flows in the range of 2.37 to 3.25 cubic metres per second (84 to 115 cu ft/s) from December to April inclusive (with a maximum in February).

At low water level, the 3 consecutive-day minimum flow can drop to 0.54 cubic metres per second (19 cu ft/s) during a five-year dry period, which is far from severe.

[6] The foundation stone for the Sollac mill was laid on 23 December 1949 in the small village of Serémange on the banks of Fensch river.

[8] The region inspired Bernard Lavilliers's Fensch Vallée, the title song of his fourth album, Les Barbares (1976).