Mount Saint Donatus, Mountain summit in eastern Slovenia.

Mount Saint Donatus is a mountain in eastern Slovenia with three peaks along a short, sharp ridge. The highest peak reaches 882 meters and holds a 10-meter cross; the eastern peak is 875 meters and the western 844 meters. The ridge is built of Lithothamnion limestone and quartz sandstone, while the base consists of soft Tertiary marl.

The mountain has been inhabited and used since prehistoric times, with Neolithic stone axes and bronze tools from around 1000 BC found near the summit. A late antique necropolis with multiple sarcophagi indicates human activity and burial practices from a later period.

The mountain's older names, Rogaška gora and Rogač, refer to its horn-like profile seen from Rogaška Slatina. The modern name, used since the 19th century, comes from the Church of Saint Donatus on the southern slope at 511 m. The church was built between 1720 and 1730 and rebuilt from 1756 to 1780 after a lightning strike in 1741 killed 59 people.

From Rudi Lodge at 590 m, an asphalted road from Rogatec (6 km, widened in 1977) reaches the saddle between Ženčaj and the main ridge; the lodge itself was built between 1976 and 1984. The serpentine trail through the primeval forest to the summit cross takes about an hour. Past the ridge, the path continues toward Mount Macelj or returns to the lodge along a secured section with a few steel cables.

The northern slope holds a beech forest with old-growth character, protected since 1965 across 27.78 hectares. Its sunny rock walls are the only known site in Slovenia for Juvan's houseleek (Sempervivum juvanii), and the endangered Hoppe's pink (Dianthus hoppei) also grows here.