Poppendorf is a former municipality in the district of Südoststeiermark, in the Austrian state of Styria. It lies in the southeastern part of the country, within the region known as Styria.
Since the 2015 Styria municipal structural reform, Poppendorf is no longer an independent municipality and is now part of the municipality of Gnas. The reform merged a number of small municipalities across the state into larger administrative units.