Hydrological monitoring data for 55 years from 1967 to 2022 for the Coalburn catchment (1.5 km2). The catchment is located in Northern England within Kielder forest, Northumberland, and is the longest running forest research catchment in the UK. In 1972/73 the upland grassland was ploughed and planted with a conifer forest. The trees are now mature and around 30% of the catchment has been felled. From 1967 to 1993 a mixture of hourly and daily data is available and from 1993 onwards all the data is hourly. The data consist of precipitation, discharge, potential evapotranspiration, other meteorological data and snow depths. The data has been extensively quality controlled and can be used for hydrological modelling or data analysis to understand the effects of forests on river flows. Full details about this dataset can be found at https://doi.org/10.5285/88d72918-324e-42a8-a4f2-bbbc322814ff