Atmospheric Greenhouse Gas Mole Fractions of CO2 and CH4 collected in Europe, covering the period 1972-2023 for CO2 and 1984-2023 for CH4, including final quality-controlled Level 2 ICOS data, release L2-2023.1. During the most recent period, a selected set of stations, after being labelled as ICOS stations, follow the ICOS Atmospheric Station specification V2.0 (https://doi.org/10.18160/GK28-2188). All concentrations are calibrated to the WMO X2019 CO2 mole fraction scale in µmole/mole (ppm), and WMO X2004A CH4 mole fraction scale in nmole/mole (ppb).