MSEA-Res: A comprehensive time-series dataset of absolute reservoir storage in Mainland Southeast Asia designed for regional planning and water management. We developed the MSEA-Res database using multi-satellite data from Landsat and Sentinel-2 at a 10-day temporal scale, spanning nearly four decades from 1985 to 2023. A Python package called ‘InfeRes’ was created and used to automatically download and process hundreds of thousands of satellite images via the Google Earth Engine Python API. The water areas from the satellite data were then translated into storage values using hypsometric curves (Area-Elevation-Storage relationship) derived from the SRTM Digital Elevation Model (DEM) and bathymetry reconstructions from the GRDL database (Hao et al., 2023) where necessary. MSEA-Res is a comprehensively validated long-term, up-to-date absolute storage database, including storage records and other relevant details from 1985 to 2023 for 185 major reservoirs (storage capacity greater than 100 million cubic meters or 0.1 km³) in Mainland Southeast Asia, totaling ~175 km³ in capacity.