This dataset consists of the global continental continuous column-averaged dry-air mole fraction of carbon dioxide (XCO2, unit: parts per million i.e., ppm) covering the period from September 2014 to December 2020. The dataset is derived from the official OCO-2 XCO2 product and incorporates data from multiple sources, including CO2 concentration data, vegetation index data, and meteorological data. We utilized a machine learning approach to generate a monthly-scale gapless CO2 product with a spatial resolution of 0.1°, stored in GeoTiff format. Please cite the following article when using the dataset: L. Zhang, T. Li, J. Wu, H. Yang, Global estimates of gap-free and fine-scale CO2 concentrations during 2014–2020 from satellite and reanalysis data, Environment International (2023), doi: https://doi.org/10.1016/j.envint.2023.108057