西格河是德国的河流，流经北莱茵-威斯特法伦和莱茵兰-普法尔茨州，属于莱茵河的右支流，河道全长153公里，流域面积2,832平方公里，平均流量每秒52立方米。

The Sieg is a river in North Rhine-Westphalia and Rhineland-Palatinate, Germany named after the Sigambrer. It is a right tributary of the Rhine and 153 kilometres in length.

The source is located in the Rothaargebirge mountains. From here the river runs southwestwards to the city of Siegen and the hills of Siegerland, both named after the river. Further west the Sieg valley forms the boundary of the Bergisches Land (northern) and Westerwald (southern). The river finally runs through a protected area east of the city of Bonn.