Kohlschwarz is a former municipality in the district of Voitsberg, in the Austrian state of Styria. It lies in the western part of Styria, within the Voitsberg district, an area of the country known for its Alpine foothills and rural landscape.
Since the 2015 Styria municipal structural reform, Kohlschwarz is no longer an independent municipality. It has been part of the municipality of Kainach bei Voitsberg since that reorganization, which merged a number of small Styrian communes into larger administrative units.
Its status as a former municipality means Kohlschwarz now exists as a cadastral community and locality within Kainach bei Voitsberg rather than as a separate administrative entity. The village and its surrounding area retain their local identity within the larger municipality.