The Mürz (German pronunciation: [mʏʁt͡s] ) is a river in Styria, Austria, with a length of 84 km (52 mi). Its drainage basin is 1,505 km (581 sq mi).

The Mürz begins at the confluence of the Stille Mürz [ceb; de; sv] and Kalte Mürz [ceb; de; sv] near Kaltenbach, Neuberg and the border to Lower Austria. It passes through Mürzzuschlag. Along its course are the tracks of the Southern Railway as well as the highway Semmering Schnellstraße [de; hu; nl; pl; sk]. The Mürz discharges into the Mur in Bruck an der Mur.