Nitrous oxide (N₂O) is the most important stratospheric ozone-depleting agent and a long-lived potent greenhouse gas with an atmospheric lifetime of more than 100 years. N₂O has been accumulating in the atmosphere since the pre-industrial period, mainly because of anthropogenic agricultural and industrial activities. There is substantial interest in estimating the contributions of individual countries to global N₂O emissions, since most nationally determined contributions (NDCs) of the United Nations Framework Convention on Climate Change set targets for N₂O. Here we present a national N₂O inventory that incorporates multiple anthropogenic and natural sources and accounts for the interaction between nitrogen additions and the biochemical processes that control N₂O emissions. We use bottom-up (process-based terrestrial biosphere model, inventory, statistical model) and top-down (atmospheric inversion) approaches to provide a comprehensive quantification of national N₂O emissions resulting from different natural and anthropogenic sources between 1980 and 2020. The results show that N₂O emissions in most countries significantly increased since 1980 due to the rising anthropogenic emissions, and China, Brazil, India, and the United States emitted the largest amount of N₂O in the recent decade. Our results can provide guidance for making country-level N₂O mitigation strategies.