The Aletsch Glacier or Great Aletsch Glacier is the largest glacier in the Alps. It has a length of about 23 km (14 mi) (2014), a volume of 15.4 km3 (3.7 cu mi) (2011), and covers about 81.7 km2 (2011) in the eastern Bernese Alps in the Swiss canton of Valais. The Aletsch Glacier is composed of four smaller glaciers converging at Konkordiaplatz, where its thickness was measured by the ETH to be still near 1 km (3,300 ft). It then continues towards the Rhône valley before giving birth to the Massa. The Aletsch Glacier is – like most glaciers in the world today – a retreating glacier. As of 2016, since 1980 it lost 1.3 kilometres (0.81 mi) of its length, since 1870 3.2 kilometres (2.0 mi), and lost also more than 300 metres (980 ft) of its thickness.

The Bernese Alps are a mountain range of the Alps, located in western Switzerland. Although the name suggests that they are located in the Berner Oberland region of the canton of Bern, portions of the Bernese Alps are in the adjacent cantons of Valais, Fribourg and Vaud, the latter being usually named Fribourg Alps and Vaud Alps respectively. The highest mountain in the range, the Finsteraarhorn, is also the highest point in the canton of Bern.