Seasonal snow is an essential source of water, especially in mountain regions. However, accurate satellite observations of the amount of snow stored in mountains are still lacking. We provide estimates of snow depth at sub-kilometer resolution over the European Alps for 2017-2019 from Sentinel-1 observations. The retrievals are based on a change detection algorithm that includes the masking of wet snow. For dry snow conditions, 300-m Sentinel-1 retrievals have a spatiotemporal correlation of 0.82 and mean absolute error of 0.19m compared with in situ measurements from 743 sites across the Alps. The results show the potential of Sentinel-1 to provide unprecedented snow estimates in regions with complex topography, where satellite observations of snow mass are currently lacking.