We present the first large-sample catchment hydrology dataset for Great Britain, CAMELS-GB (Catchment Attributes and MEteorology for Large-sample Studies). CAMELS-GB integrates a wealth of spatial and time-varying datasets formulated from national, continental and global products based on observational, satellite and derived data. CAMELS-GB consists of hydro-meteorological timeseries, catchment attributes and catchment boundaries for 671 catchments that cover a wide range of climatic, hydrological, landscape and human management characteristics across Great Britain. Daily timeseries covering 1970-2015 (a period including a number of hydrological extreme episodes) are provided for a range of hydro-meteorological variables including rainfall, potential evapotranspiration, temperature, radiation, humidity and river flow. A comprehensive set of catchment attributes are quantified including topography, climate, hydrology, land cover, soils and hydrogeology. Importantly, we also derive human impact attributes (including attributes summarising abstraction returns and reservoir capacity in each catchment), as well as attributes describing the quality of the flow data (including the first set of discharge uncertainty estimates for Great Britain). CAMELS-GB is intended for the community as a publicly available, easily accessible dataset to use in a wide range of environmental and modelling analyses.