The A4240 is a short, largely urban A-road in south Wales.
The road starts at a roundabout on the A48 just to the west of M4 J47. It heads west through Penllergaer, descending steeply past the houses to reach a retail park. There's a mini-roundabout followed immediately by a full roundabout, from where a minor road heads south to Garngoch Hospital, after which a brief semi-rural section leads to a bridge over the Afon Lliw. The next settlement, Gorseinon, starts just before the river is crossed.
We continue west through the town, running along the High Street to cross the B4296 at traffic lights. The road now becomes residential and we move into seamlessly into Loughor where there's a sharp left-hand bend. At the next roundabout we meet the B4620 (former A4070) and continue through the centre of town. We climb past the castle ruins and then descend again to a roundabout on the A484. Immediately right is a bridge over the River Loughor and the estuary lies ahead.
The road was originally part of the A48 then became the eastern end of the A484 when the former was rerouted in 1935. The A4240 number came about when the A484 was moved onto the present bypass.