The N33 is one of the newest of Ireland's primary N-roads. It opened in 2001 and was signposted from the beginning as the N33. The route was described as "proposed" in the 1994 listing, but does not seem to have been formally named the N33 until 2006. It was built to join the then new M1 to the N2. Other than close to the junctions at either end, the route closely parallels the route of the former Ardee branch of the Great Northern Railway (Ireland). The disused railway bed forms a pedestrian path along the south side of the N33.