The N3 road is a national primary road in the Republic of Ireland, running between Dublin, Cavan and the border with County Fermanagh. The A509 and A46 roads in Northern Ireland form part of an overall route connecting to Enniskillen, and northwest to the border again where the N3 reappears to serve Ballyshannon in County Donegal.

Rush hour congestion between Navan and Dublin city was very heavy (up to 22,000 vehicles per day on single carriageway portions of the N3 in 2002), and problems occurred at most built-up areas between these points. A tolled motorway bypass replacement, the M3 motorway, was opened to traffic on 4 June 2010.

The former section from its junction with the M50 to Dublin city centre, as well as the bypassed section from Clonee to the border with County Cavan, have been reclassified as the R147 road.