Oberhaag is a municipality in the district of Leibnitz, in the Austrian state of Styria. It lies in the southern part of Styria, a region known as the Leibnitz district, which borders Slovenia to the south.
As a municipality, Oberhaag is one of the smaller administrative units within the district, encompassing the village itself along with surrounding rural settlements and countryside. The area forms part of the broader cultural and geographic landscape of southern Styria, a region historically shaped by agriculture and its position near the Austrian-Slovenian border.
Oberhaag is situated within the district of Leibnitz, whose administrative centre is the town of Leibnitz. The municipality shares the district's general characteristics, including its location in the hilly terrain of southern Styria and its proximity to the border region.