The Aletschhorn (4,194 m (13,760 ft)) is a mountain in the Alps in Switzerland, lying within the Jungfrau-Aletsch region, which has been designated a World Heritage Site by UNESCO.

Standing thus between the principal range of the Bernese Alps and the Pennine chain, it shares with the Bietschhorn the advantage of occupying a central position in relation to the high peaks around it.

Its remote location in the middle of glaciers means that the Aletschhorn, despite its height, is less frequently visited and less well known than the summits of the Jungfrau and the Eiger, which lie about 10 km on the north.

The party passed the night in some holes in the rocks above the Mittel Aletsch Glacier (on the east side of the mountain), and on the following morning, on 18 June, started the ascent and reached the snow arête connecting the Dreieckhorn with the main peak.

The passage along this arête at a so early period of the year, before the snow has become well consolidated, involved some risk and a slope of névé lying at an angle of 50°, required care and good step-cutting.