The value of satellite remotely sensed data is especially relevant in the context of global hydrological modelling, which provides important information on the status and spatio-temporal changes of water resources worldwide. Satellites can be used to monitor the water cycle under human impact, to calculate the fluxes of water through rainfall, surface and groundwater runoff, evaporation, transpiration and condensation. Using the water balance equation as a basis, we discuss in detail the Gravity Recovery and Climate Experiment (GRACE) mission and a small sample of other contributing missions, such as the Surface Water Ocean Topography (SWOT), Soil Moisture and Ocean Salinity (SMOS), Soil Moisture Active Passive (SMAP), Tropical Rainfall Measuring (TRMM), Global Precipitation Measurement (GPM), Clouds and the Earth’s Radiant Energy System (CERES) and Moderate Resolution Imaging Spectroradiometer (MODIS). We conclude the chapter with perspectives and requirements for the future, and we stress the need for continuous, long-term monitoring of the global water cycle from space.