2021-1 release containing data from the atmospheric network of ICOS Research Infrastructure for 26 stations and 67 vertical levels at Gartow, Helgoland, Hohenpeißenberg, Hyltemossa, Ispra, Jungfraujoch, Karlsruhe, Křešín u Pacova, La Réunion, Lampedusa, Lindenberg, Lutjewad, Monte Cimone, Norunda, OPE, Ochsenkopf, Pallas, Puy de Dome, Saclay, SMEAR-II Hyytiälä, Steinkimmen, Svartberget, Torfhaus, Trainou, Utö - Baltic Sea and Zeppelin Observatory. This collection contains the final quality controlled hourly averaged data for the mole fractions of CO2, CH4, N2O, CO and meteorological observations measured at the relevant vertical levels of the measurements stations, and where available 14C in CO2 in two-weekly integrated samples, for the period September 2015-January 2021. All stations follow the ICOS Atmospheric Station specification V2.0 (https://doi.org/10.18160/GK28-2188) and are certified as ICOS atmospheric stations Class I or II. Data processing has been performed as described in Hazan et al., 2016 (doi:10.5194/amt-9-4719-2016).