Ság Mountain, Volcanic mountain in Celldömölk, Hungary.

Ság Mountain is a 279-metre volcanic butte rising about 150 metres above Celldömölk in Vas County, Hungary. Its lower slopes are sandy Pannonian sediments, while the upper cone consists of volcanic tuff and a 50-metre-thick basalt cap. Quarrying has left spoil heaps and inner quarry yards, and the Ság Volcano Trail exposes the lava solidified in the vent of the last eruption.

Ság is the eroded remnant of a volcano active about five million years ago, when lava solidified into a 50-metre basalt cap over tuff and sandy Pannonian layers. Romans quarried its basalt for the Amber Road and the roads of Savaria. Modern quarrying began with the Sághegyi Bazaltbánya Rt. in 1909, ran at full scale from 1911 and ended in 1957 after some 17 million tonnes of stone had been removed.

The mountain served as a filming location for Farthen Dûr in the Eragon movie adaptation, making it recognizable to fans of the fantasy film.

The Ság Vulkánösvény geological trail crosses the former basalt quarry, where the lava solidified in the vent of the last eruption can be seen. The summit plateau holds the cross-shaped Trianon memorial and the 1971 basalt column commemorating Eötvös Loránd's 1891 measurements. The Sághegyi Museum in a restored mine building and the Kemenes Vulkán Park in its garden are at the foot of the hill.

The 148 metres is the hill's height above the surrounding plain, not its prominence: the summit lies at 279 metres, and the town of Celldömölk spreads around its slopes in a semicircle. Eötvös Loránd measured here in 1891 with his torsion balance, and a basalt column by Antal Károly, set up in 1971, marks the spot.