|Length:||6 miles (9.7 km)|
|Route outline (key)|
The A4043 runs parallel to the Afon Lwyd south of the Monmouthshire town of Blaenavon.
The road starts in the centre of Blaenavon by turning off the B4246, making it a member of the small group of A-roads that starts on a B-road. It follows the river (and the B4246) southwards, crossing the former in Cwmavon and the latter in Abersychan.