Saint-Sorlin glacier (SSO) is located in the Arvan valley, between 2700 and 3400 m altitude. The glacier is situated in the Grandes Rousses massif, and one of the glaciers with longest records of glacier mass balance worldwide. Data series are continuous and cover few decades (more than 50 years of mass balance measurements).This site is also characterized by the complete glaciological parameters performed annually to complete annual and seasonnal mass balance : ice velocity, ice thickness variation, snout position.In addition, meteorological observations complete the data base. 1 weather station, running since 2005, is located on the moraine, close to the snout of the glacier. SSO is a part of the French Glacier Observatory GLACIOCLIM/CRYOBS-CLIM.