Ammonia is a form of reactive nitrogen whose emissions are primarily from livestock excreta and crop fertilisation. Atmospheric ammonia is a major source of anthropogenic aerosols, and can negatively impact both human and ecosystem health. Despite its importance, rates of ammonia emission remain highly uncertain at all spatial scales, local to global. Here we use satellite ammonia observations to produce the first global observation-based, county-level annual rates of ammonia emissions. We find that previously reported ammonia emissions tend to be under-estimated over large parts of the globe. Global satellite-based emission totals are 1.8 times greater than in previously reported anthropogenic locations, and 4 times greater when newly detected anthropogenic and natural sources are included. Countries with ammonia regulations in place (e.g. European Union) tend to show a much better comparison to reported emissions. In addition to quantifying ammonia emissions and their spatial distribution, our satellite-based methodology provides a globally consistent emissions database that is not subject to offsets and gaps across geopolitical borders. With ammonia emissions expected to rise in the future due to increasing demands to feed the growing world population, there is a growing need for timely monitoring of ammonia emissions at a county-level worldwide to support mitigation policies.