Althofen is a town in the district of Sankt Veit an der Glan in the Austrian kingdom of Carinthia. The town is located approximately 15 km north of Sankt Veit an der Glan and 30 km north of the country capital Klagenfurt within the Krappfeld Valley between the Gurktal Alps mountain variety in the west and the Lavanttal Alps within the east. The township includes the cadastral communities Treibach, Althofen, and Toscheldorf. There are a few prehistoric finds in Althofen, particularly two Neolithic axes, some Late Bronze Age ceramics and a Hallstatt Age tumulus. Several small reveals and a few tombstones date from the Roman generation.
From about 600 Althofen became a settlement place of Slavic human beings. Altanhouun within the Duchy of Carinthia changed into first noted in a 1041 deed. Like in neighbouring Friesach, the estates had been held by using the Archbishops of Salzburg. The nearby Salzburg bailiffs resided at Althofen Castle, which became devastated in the 15th century Austrian–Hungarian War and rebuilt from about 1500 because the Neues Schloss under Prince-Archbishop Leonhard von Keutschach.