The B26 was a medium-length B-road in south County Down.
The road started on the A2 on the northern edge of the coastal town of Newcastle and then headed northwest to Castlewellan, where there was a short multiplex west along the A25. There was another, longer, multiplex, this time along the B25, starting a few miles further on in the centre of Katesbridge.
After continuing alongside the River Bann the end of the B26 was reached on the A1 (now A26) in the centre of Banbridge.
The B26 did not last long, being upgraded to Class I status in the mid-1920s. It became part of the A50, which it remains.