The Aletsch Glacier (German: Aletschgletscher) or Great Aletsch Glacier (German: Grosser Aletschgletscher) is the largest glacier in the Alps. It has a length of about and covers more than in the eastern Bernese Alps in the Swiss canton of Valais. The Aletsch Glacier is composed of three smaller glaciers converging at Concordia, where its thickness was measured by the ETH to be near . It then continues towards the Rhône valley before giving birth to the Massa.