Geistthal 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, a largely rural and mountainous area of the country.
As part of the 2015 Styria municipal structural reform, Geistthal ceased to be an independent municipality and was merged into the newly formed municipality of Geistthal-Södingberg. Since that reform, it has been a constituent part of Geistthal-Södingberg rather than a separate administrative unit.
Its administrative history is therefore defined chiefly by this merger, which placed the former municipality within the larger combined municipality alongside Södingberg. Geistthal remains identified with the Voitsberg district and the state of Styria in Austria.