Sosto, Mountain summit in Ticino, Switzerland

The Sosto is a 2,220.6 m gneiss mountain of the Swiss Lepontine Alps in Ticino, overlooking Olivone and Campo in the Blenio valley. Its steep west and south flanks form a freestanding rock pyramid nicknamed the Matterhorn of the Blenio valley, while the north and east sides above Val Luzzone and Val Carassin drop less sharply. At the foot of the west wall the Brenno has cut the narrow Gola del Sosto gorge.

The Sosto appears on Olivone's coat of arms, drawn schematically in red. The old road Vecchia Strada del Sosto to Campo ran through the Gola del Sosto gorge at the foot of the west wall before a tunnel replaced it. The mountain gives its name to the Sosto Schiefer, a blue-grey limestone mica schist with chert and marble layers that forms a fourth-order sub-unit in Alpine geology.

The Sosto appears in red on the coat of arms of Olivone, the village it overlooks, so the peak is a local emblem as well as a landmark. Its nickname, Matterhorn of the Blenio Valley, comes from its isolated rock-pyramid form with steep west and south faces.

The easiest ascent starts at Passo Muazz (1,697 m), reachable by car from Lago di Luzzone; an unmarked trail climbs steeply to a 2,102 m sub-summit, then crosses rock to the top, rated T4 to T5. From Olivone a material cable car serves Alp Cumpiètt (1,570 m), from where a path runs north past the pass.

The Sosto gives its name to a geological sub-unit: the blue-grey Kalkglimmerschiefer with cherty limestone and marble layers found in its summit region is known as Sosto schist, part of the Bündnerschiefer. The mountain also appears schematically in red on the coat of arms of Olivone.