N51 road
Bóthar N51
N51 leaving Athboy
Route information
Length	52.994 km (32.929 mi)
Location
Country	Ireland
Primary destinations	(bypassed routes in italics) County Westmeath Delvin, leaves N52 Crosses the Stoneyford River County Meath Athboy - R154 Crosses the Athboy River Boyerstown - Junction with the M3 motorway Navan - R161 N3 R153 R162 Navan - Crosses the River Blackwater R163 Slane - N2 County Louth Joined by the R168 regional road; crosses the M1; R168 leaves Drogheda Terminates at a roundabout on the R132
Highway system
Roads in Ireland Motorways Primary Secondary Regional

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 (now by-passed by the M1 motorway) and is of a higher standard than most regional roads.

Upgrade

On 15 May 2009 Phase 2B of the N51 Navan Inner Relief Road was opened to traffic. This route provides a direct link between the N3/M3 Kells Road and the N51 Athboy Road. On the same day a further 3.9 kilometres of the realigned N51 which has been constructed as part of the M3 motorway scheme was opened to traffic, 2.5 kilometres of which is Type 1 dual carriageway.