The Gorner Glacier 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 12.4 km long and 1 to 1.5 km wide. The entire glacial year of the glacier related to Gorner Glacier is 83 km², which makes it the second largest glacial system in the Alps after the Aletsch Glacier system; however it ranks only third in length behind the Aletsch and Fiescher Glacier, respectively. Numerous smaller glaciers connect with the Gorner Glacier. Its tributaries are: Gornergletscher, Monte Rosa Gletscher, Grenzgletscher, Zwillingsgletscher, Schwärzegletscher, Breithorngletscher, Triftjigletscher, and Unterer Theodulgletscher.
The Grenzgletscher between the central Monte Rosa massif and the Liskamm to the south is nowadays by far the lower Gorner Glacier's main tributary. The Gorner Glacier's upper part is almost already disconnected from its lower part. Also the former tributaries Breithorngletscher, Triftjigletscher, and Unterer Theodulgletscher lost their connections to the Gorner Glacier during the last century; the Lower Theodul Glacier became disconnected in the 1980s.