Osterwitz is a former municipality in the district of Deutschlandsberg, in the Austrian state of Styria. It lies in the western part of Styria, in the Deutschlandsberg district, a hilly region of southern Austria near the border with Slovenia.
Since the 2015 Styria municipal structural reform, Osterwitz is no longer an independent municipality and has been part of the municipality of Deutschlandsberg. The reform merged a number of small municipalities across Styria into larger administrative units.
Prior to that merger, Osterwitz existed as a municipality in its own right within the same district. Its administrative incorporation into Deutschlandsberg means that local governance is now handled at the level of the larger municipality.