Concentrations of gaseous and aqueous fixed nitrogen products and isotopic measurements of aqueous nitrite and nitrate in spark discharge experiments. Spark experiments were conducted at the University of St Andrews in the St Andrews Isotope Geochemistry Lab (StAIG) between November 2020 and February 2022. Analysis of gaseous products was carried out with a quadrupole mass spectrometer (Hiden Analytical ExQ Quantitative Gas Analyser) in St Andrews. Measurement of concentrations of aqueous nitrite and nitrate and their isotopic composition were carried out for one part of the samples in St Andrews and for the other part at Brown University, Rhode Island, USA. The data was collected to investigate the efficiency of nitrogen fixation by lightning in different gas compositions, resembling the atmospheres of modern and early Earth. The isotope data was used to determine the role of lightning in the delivery of nutrients to the earliest ecosystems on Earth by comparing our results to measurements of sedimentary rock samples from the Archean. The experimental set up was built by Patrick Barth and Eva E. Stüeken, the experiments were conducted by Patrick Barth, Lukas Rossmanith, and Yuqian Peng, the analysis conducted by Patrick Barth, Lukas Rossmanith, Yuqian Peng, and Wendell Walters with support from Mark Claire, and the data was analysed by Patrick Barth, Eva E. Stüeken, Christiane Helling, and Wendell Walters. This dataset includes all data that is reliable and was used in the accompanying publication.