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, all in County Meath, before crossing the M1 motorway and terminating near Drogheda in County Louth at a roundabout on the R132.