The A5110 was a short A-road along the Conwy Valley in North Wales.
The road started on the A55 by the castle in Conwy. It squeezed through the castle walls and under the railway line before following a winding road to the south. It went over a ridge between the Gyffin and Conwy rivers before descending to a saddle point. Here the road turned left, with the B5106 continuing south. The A5110 followed a narrow, winding road with good views over the Conwy Valley to the left.
Presently the road descended into the valley where it met the B5279 immediately to the west of a bridge over the Conwy, the first one upstream from Conwy, which the A5110 crossed. On the far side it crossed the Conwy Valley Line at a level crossing by Tal-y-Cafn station and ended shortly afterwards on the A496 (now A470).
The original number of the road south of Conwy along the valley was the B4407; this was renumbered B5106 in 1935. In the same year, the short road across the valley west of Tal-y-Cafn was classified as the B5279. The A5110 was created in the 1950s, taking over the northern end of the B5106 and the river crossing of the B5279, together with an unclassified section cutting off the corner between the two. This renumbering seems to have been undone in the 1960s, with the three sections of road reverting to the numbers they had had before the A5110 came into being. Given that the unclassified section deserves to be it is not clear why the A5110 existed in the first place.