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Quantifying global patterns of terrestrial nitrogen (N) cycling is central to predicting future patterns of primary productivity, carbon sequestration, nutrient fluxes to aquatic systems and climate forcing. With limited direct measures of soil N cycling at the global scale, syntheses of the ¹⁵N:¹⁴N ratio of soil organic matter across climate gradients provide key insights into understanding global patterns of N cycling. In synthesizing data from over 6000 soil samples, we show strong global relationships among soil N isotopes, mean annual temperature (MAT), mean annual precipitation (MAP) and the concentrations of organic carbon and clay in soil. In both hot ecosystems and dry ecosystems, soil organic matter was more enriched in ¹⁵N than in corresponding cold ecosystems or wet ecosystems. Below a MAT of 9.8°C, soil δ¹⁵N was invariant with MAT. At the global scale, soil organic C concentrations also declined with …