Irschen is a municipality in the district of Spittal an der Drau in the Austrian state of Carinthia. It consists of the Katastralgemeinden Irschen, Ritterdorf and Simmerlach. It is situated on the northern slope of the Upper Drava Valley, near the B 100 Drautal Straße highway and the Drautalbahn railway line.
A settlement area since the Early Iron Age (Hallstatt Culture), Irschen may be identical to the Idunum polis in the former Celtic kingdom of Noricum, as mentioned in Ptolemy's Geographia. In Roman times a mansio laid on the road leading over the Gailbergsattel mountain pass to Italia. Ursus I, Patriarch of Aquileia probably built a first church about 810 in the place then called Ursen, which was mentioned as Castrum Ursen in a 1086 deed. In medieval times Irschen was a mining area, especially for gold.