The Gorner Glacier (German: Gornergletscher) is a valley glacier found on the west side of the Monte Rosa Massif close to Zermatt in the canton of Valais, Switzerland. It is about 14 km (8.7 mi) long and 1 to 1.5 km (0.62 to 0.93 mi) wide. The entire glacial area of the glacier related to Gorner Glacier is 57 km2 (22 sq mi) (1999), which makes it the second largest glacial system in the Alps after the Aletsch Glacier system. Numerous smaller glaciers connect with the Gorner Glacier. Its tribunaries are: Gornergletscher (after which the whole system is named), Grenzgletscher, Zwillingsgletscher, Schwärzegletscher, Breithorngletscher and Theodulgletscher (although this one is actually disconnected now); also Monte Rosa Glacier used to be connected. The main tributary is the Grenzgletscher.