The length of streamflow records is generally limited to the last 50 years. It therefore prevents studying the long-term evolution of streamflow regimes. In order to overcome this limit, this work takes advantage of a 140-year ensemble hydrometeorological dataset over France based on: (i) a probabilistic precipitation and temperature downscaling of the global Twentieth Century Reanalysis over France (Caillouet et al., 2016a), and (ii) a continuous hydrological modelling that uses the high-resolution meteorological reconstructions as forcings over the whole period (Caillouet et al., 2016b). The resulting SCOPE Hydro dataset provides an ensemble of 25 equally plausible daily streamflow time series for a reference network of more than 600 stations in France over the 1871-2012 period. A subset of 184 stations located in all French mountain ranges (Alps, Pyrenees, Massif Central, Jura and Vosges) is specifically targeted here. This work aims at studying the long-term evolution of streamflow in mountainous catchments where the regime is largely influenced by snow accumulation and snowmelt processes. Results show a high interannual variability of the seasonal snowmelt component of streamflow, pondered by a relatively large multidecadal variability highlighting periods with large (1910s) or small (1950s, post-1980 period) snowmelt.