Data accompanying the manuscript "Nitrogen fixation in mesoscale eddies of the North Pacific Subtropical Gyre: patterns and mechanisms", submitted to Global Biogeochemical Cycles. Datasets refer to the 2017 MESO-SCOPE and 2018 Hawaiian Eddy Experiment cruises by the year of the expedition. Contents include: - Environmental measurements, such as temperature, concentrations of phosphates (PO43-) and dissolved iron (DFe), and scalar photosynthetically active radiation (PAR), from the transect and eddy center stations (see Eddies_environmental_datasets.xlsx). -N2-fixation rates (NFR) measured on in-situ arrays deployed in eddy centers (see Eddies_NFR_datasets.xslx) -nifH gene abundances measured in eddy centers and eddy transect (2017) (see Eddies_nifH_datasets.xlsx) -Diazotroph cell abundances measured by automated flow cytometry (FCM) in eddy centers (see Eddies_FCM_datasets.xlsx) -Diazotroph interpolated growth rate predictions derived from the ecophysiological model forced by in situ environmental data (see Eddies_interpolated_growthrates.xlsx) -Predator-prey model input/output including putative grazer abundances, grazing rate estimates, interaction and correlation matrices, and sensitivity analysis of the model (see Eddies_grazing_datasets.xlsx) -Trichodesmium optical/size properties measured by imaging flow cytometry in eddy centers and a surface bloom sampled in 2017 (see Eddies_Trichodesmium_properties.xlsx)