Kapfenberg is a city in the Bruck-Mürzzuschlag District of the Austrian state of Styria. It lies in the Mürz valley in Upper Styria, between Bruck an der Mur and Kindberg, and forms part of one of the main industrial and transport corridors of central Styria.
With 21,964 residents with a main residence as of 30 September 2024, it is the third-largest city in Styria after Graz and Leoben.