Sustenhorn, Alpine summit in Uri Alps, Switzerland

Sustenhorn is a 3,503-metre summit in the Uri Alps on the border of the cantons of Bern and Uri, overlooking Susten Pass 3.5 km to the north. Its west flank above Innertkirchen is almost entirely covered by the Stein Glacier, while the steeper east side above Göschenen carries the smaller Wallenburfirn and Flachensteinfirn. The massif includes the Vorder Sustenhorn (3,318 m), Chli Sustenhorn (3,309 m) and Sustenlimihorn (3,316 m).

The Sustenhorn was first climbed in 1851 by a party that set out from Innertkirchen, on the Bernese side of the mountain. The 3,503 m summit lies on the border of the cantons of Bern and Uri, 3.5 km south of the Susten Pass that gives it its name.

The name Sustenhorn derives from the Susten Pass, 3.5 km to the north, which the mountain overlooks from the south. The standard ascent from the Bern side starts at Hotel Steingletscher and passes the Tierberglihütte; from Uri, climbers start at Göscheneralpsee and use the Chelenalphütte. The Voralphütte serves the harder east-ridge route over gneiss rock.

The normal route starts from Hotel Steingletscher on the Bern side and reaches the summit via the Tierbergli Hut; the SAC rates it L (easy) with no climbing sections. An alternative from Göscheneralpsee via the Chelenalphütte and Sustenlimi (3,078 m) is also rated L but has a short grade I (UIAA) climb. The east route over the Flachensteinfirn is rated WS, while the east ridge from the Voralphütte is ZS with climbing up to grade IV on gneiss.

The Sustenhorn's east ridge, dropping toward the Voralptal, is the hardest way up: the SAC rates the combined route from the Voralphütte as ZS, with climbing up to grade IV on gneiss. The easier normal route from the Hotel Steingletscher via the Tierberglihütte is rated L.