Which Swiss glacier is the largest glacier in the Alps?

The Swiss glacier that is the largest glacier in the Alps is the Aletsch Glacier.

Also called the Great Aletsch Glacier, it lies in the Bernese Alps of Switzerland, mainly in the canton of Valais. Four major ice streams converge at the Konkordiaplatz, creating the broad glacier that flows south toward the Rhône Valley and feeds the Massa River.

The glacier measured about 23 kilometres long and covered roughly 81.7 square kilometres in measurements from the early 2010s. Its ice is exceptionally thick: more than 900 metres has been measured near the Konkordiaplatz. The surrounding Jungfrau-Aletsch region became a UNESCO World Heritage Site in 2001.

A common mix-up is confusing the largest glacier with the longest glacier in a particular Alpine country. The Aletsch is the Alps' largest by area and is also among their longest, but glaciers such as the Gorner Glacier and Fiescher Glacier are separate, smaller ice systems. Like most Alpine glaciers, Aletsch has been retreating substantially since the nineteenth century.