Sulm, River, Styria, 83 km long tributary of the River Mur; its sources, the Schwarze Sulm and the Weiße Sulm, merge at Prarath (alt. 304 m); approx. half-way down the river lies the municipality of Gleinstätten (alt. 308 m). The River Sulm is joined by the River Saggau (Saggau Valley) at Großklein (alt. 321 m) and by the River Laßnitz near Leibnitz (alt. 274 m). At Leibnitz the River Sulm has an average flow rate of 16.3 m3/sec. Close to Seggauberg (alt. 366 m) lies the small Sulm-See lake; the River Sulm flows into the River Mur near Retznai (alt. 261 m). Between Sulm and Laßnitz lie the Sausal Hills (viniculture).