Piz Buin, Mountain peak in Silvretta range, Austria and Switzerland

Piz Buin is a 3,312-metre peak of dark rock and clinging snow in the Silvretta, on the border between Vorarlberg and Graubünden. Its angular summit narrows to a point, with a shoulder on the left and a longer ridge falling away to the right. The nearby Kleiner Piz Buin (3,255 m) is a separate summit, not a second top of this mountain.

Piz Buin was first climbed on 14 July 1865 by Joseph Anton Specht and Johann Jakob Weilenmann, guided by Jakob Pfitscher and Franz Pöll. The nearby Piz Buin Pitschen, 3,255 m, was climbed three years later. The border between Vorarlberg and Graubünden runs east-west across the summit.

The Romansh name Piz Buin Grond means "Great Piz Buin", while the neighbouring 3,255 m summit is Piz Buin Pitschen, "Small Piz Buin". The Ill river rises from the Ochsental and Vermunt glaciers on the mountain's Austrian flanks and flows north to the Silvretta reservoir. The summit holds an old wooden cross.

The climb requires crossing the Vermunt glacier from the Wiesbadener hut, followed by a traverse across the Ochsentaler glacier. Good weather and glacier experience are essential for a safe ascent to this high peak.

The summit holds an old wooden cross, reached after a zigzag walk from the Buin gap with a single 20 m steep step. The Austria-Switzerland border runs east to west across the flat summit space. The glacier buttercup flowers even at the top.