N51 road (Ireland)
The N51 road is a national secondary road in Ireland.
West to east, it starts in Delvin, County Westmeath at a junction with the N52. It passes through Athboy, a junction with M3 motorway, Navan and Slane, where it crosses the N2 road, all in County Meath, before crossing the M1 motorway and terminating near Drogheda in County Louth at a roundabout on the R132.
It is an unusual arrangement for a national secondary road to terminate at a regional road. However the R132 is the former N1 route and is of a higher standard than most regional roads.