An overview is provided of the knowledge regarding the vascular flora of Alto Adige or South Tyrol, Italy’s northernmost province, gained through its thorough study during the last decades, primarily by means of comprehensive floristic mapping. The flora of South Tyrol comprises some 2600 taxa, 83% of which are classified as indigenous or archaeophytic. Of the remaining 17% alien species, 7% are considered as naturalized and 10% as casual. A detailed analysis of the composition of the flora reveals a huge proportion of species with a pan-European distribution range, of species with the main area of distribution in the nemoral zone, or in the zone of European high mountains (alpid), or in the sub-Mediterranean region, and of Alpine species. This reflects the geographic location of the region both in the southern part of Central Europe and in the midst of the Alps. One phytogeographical particularity is the relatively high proportion of arctic-alpine, boreal and pontic elements, which is due to postglacial migrations and associated area disjunctions and, in the case of pontic elements, to particularly favorable microclimates in parts of South Tyrol.