Watershed urbanization, an integrated anthropogenic perturbation, is another considerable global concern in addition to that of global warming and may significantly enrich the N loadings of watersheds, which then greatly influences the nitrous oxide (N 2 O) production and fluxes of these aquatic systems. However, little is known about the N 2 O dynamics in human-dominated metropolitan river networks. In this study, we present the temporal and spatial variations in N 2 O saturation and emission in the Chongqing metropolitan river network, which is undergoing intensified urbanization. The N 2 O saturation and fluxes at 84 sampling sites ranged from 126% to 10536% and from 4.5 to 1566.8 μmol N 2 O m −2 d −1 , with means of 1780% and 261 μmol N 2 O m −2 d −1 . The riverine N 2 O saturation and fluxes increased along with the urbanization gradient and urbanization rate, with disproportionately higher values in urban rivers due to the N 2 O-rich sewage inputs and enriched in situ N substrates. We found a clear seasonal pattern of N 2 O saturation, which was co-regulated by both water temperature and precipitation. Regression analysis indicated that the N substrates and dissolved oxygen (DO) that controlled nitrogen metabolism acted as good predictors of the N 2 O emissions of urban river networks. Particularly, phosphorus (P) and hydromorphological factors (water velocity, river size and bottom substrate) had stronger relationships with the N 2 O saturation and could also be used to predict the N 2 O emission hotspots in regions with rapid urbanization. In addition, the default emission factors ( EF5-r ) used in the Intergovernmental Panel on Climate Change (IPCC) methodology may need revision given the differences among the physical and chemical factors in different rivers, especially urban rivers.