The ECOSTRESS/OCO-3 (“ECOCO3”) data set consists of spatially and temporally co-located observations from the ECOsystem Spaceborne Thermal Radiometer Experiment on Space Station (ECOSTRESS) and the Orbiting Carbon Observatory 3 (OCO-3) instruments currently operating on the International Space Station. Land Surface Temperature, Evapotranspiration, and Water Use Efficiency data products from ECOSTRESS, and Solar-Induced Chlorophyll Fluorescence and Dry-Air Column Mole Fraction CO2 from OCO-3 are matched in space and time over 3°x3° areas across the globe where OCO-3 performs Snapshot Area Map and Target mode observations. The original, native resolution data products are filtered for data quality and spatially averaged onto a 0.005°x0.005° uniform grid, i.e., 557m x 557m or 0.3km2 at the Equator. The aim of the ECOCO3 product is to provide users with synergistic, high-quality data of terrestrial vegetation and atmospheric parameters, for easy and ready use in scientific analysis and modeling. The initial V1.0 release is based on ECOSTRESS Collection 1 and OCO-3 Version 11 data products, for the common measurement period of August 2019 through January 2023, from the start of OCO-3 observations through the end of ECOSTRESS Collection 1.