High resolution nitrogen (N) deposition maps were developed to assess the exceedance of empirical critical loads of nutrient N for grasslands in Ireland. Nitrogen emissions have remained relatively constant during the past 20yrs and are projected to remain constant under current legislation. Total N deposition (estimated as wet nitrate [NO 3 − ] and ammonium [NH 4 + ] plus dry NO × and NH 3 ) ranged from 2 to 22kgNha −1 yr −1 (mean=12kgNha −1 yr −1 ) to grasslands. Empirical critical loads for nutrient N were set at 15kgNha −1 yr −1 for both acid and calcareous grasslands; exceedance was observed for ~35% (~2311km 2 ) of mapped acid grasslands. In contrast, only ~9% of calcareous grasslands (~35km 2 ) received N deposition in excess of the critical load. Reduced N deposition (primarily dry NH 3 ) represented the dominant form to grasslands (range 55–90%) owing to significant emissions associated with livestock (primarily cattle). The extent of exceedance in acid grasslands suggests that N deposition to this habitat type may lead to adverse impacts such as a decline in plant species diversity and soil acidification. Further, given that elevated N deposition was dominated by NH 3 associated with agricultural emissions rather than long-range transboundary sources, future improvements in air quality need to be driven by national policies.