Radenthein (Slovene: Radenče) is a town in Spittal an der Drau District, in the Austrian state of Carinthia.

The town is situated in the Gegend valley (Gegendtal) of the Nock Mountains range (part of the Gurktal Alps), stretching to the eastern shore of Lake Millstatt.

The municipal area comprises the cadastral communities of Döbriach, Kaning, Laufenberg, Radenthein proper, Sankt Peter, and Tweng.

A chapel at villam Ratehtim was first mentioned in an 1177 deed, then part of the Millstatt Abbey estates within the Duchy of Carinthia; it was raised to a parish in 1262.

Since the Middle Ages Radenthein had been an iron ore and garnet mining area and the site of a finery forge, even the use of reverberatory furnaces is documented since the late 18th century.