This dataset comprises data from the GEMStat database that are available under an open data license (CC BY 4.0 or equivalent). It is made available on the Zenodo repository. GEMStat provides access to freshwater quality data. The data are voluntarily provided by countries and organizations worldwide within the framework of the GEMS/Water Programme of the United Nations Environment Programme (UNEP). The dataset includes more than 20 Million measurement from over 13,000 stations and covering more than 600 different parameters and spans the time period from 1906 to 2023. This represents over 70% of all GEMStat data, further data is only available under more restricted data licenses. GEMStat is operated by the GEMS/Water programme of the United Nations Environment Programme (UNEP) and hosted at the International Centre for Water Resources and Global Change (ICWRGC) and the German Federal Institute of Hydrology (BfG). The data in GEMStat is provided by National Hydrological Services of UN member states.