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The continuous growth of atmospheric nitrous oxide (N2O) is of concern for its potential role in global warming and future stratospheric ozone destruction. Climate feedbacks that enhance N2O emissions in response to global warming are not well understood, and past records of N2O from ice cores are not sufficiently well resolved to examine the underlying climate‐N2O feedbacks on societally relevant time scales. Here, we present a new high‐resolution and high‐precision N2O reconstruction obtained from the Greenland NEEM (North Greenland Eemian Ice Drilling) and the Antarctic Styx Glacier ice cores. Covering the N2O history of the past two millennia, our reconstruction shows a centennial‐scale variability of ~10 ppb. A pronounced minimum at ~600 CE coincides with the reorganizations of tropical hydroclimate and ocean productivity changes. Comparisons with proxy records suggest association of centennial‐ to millennial‐scale variations in N2O with changes in tropical and subtropical land hydrology and marine productivity. Plain Language Summary: Nitrous oxide (N2O) is a greenhouse and ozone‐depleting gas. The growing level of N2O in the atmosphere is of global concern, and records of past N2O variations can provide an important context for understanding the links between N2O and climate change. In this study, we report new, high‐quality N2O records covering the last two millennia using ice cores obtained from Greenland and Antarctica. Our N2O records show rapid centennial‐scale changes in atmospheric N2O and confirm a pronounced minimum near 600 CE. Comparison with climate records suggests that hydroclimate change on land and changes in marine productivity contribute to centennial‐ to millennial‐scale N2O variations. Key Points: We report records of N2O concentration for the last 2,000 yr from the Styx ice core in Antarctca and NEEM ice core in GreenlandThe data accurately reveal the timing and magnitude of N2O variations on centennial time scalesVariations in N2O are associated with changes in tropical and subtropical land hydrology and marine productivity [ABSTRACT FROM AUTHOR]