|Length:||20.6 miles (33.2 km)|
|Meets:||A487, B4329, A40, A478|
|Route outline (key)|
The B4313 is a long B-road in east Pembrokeshire. It was originally unclassified but gained its number in 1935.
The road starts out in the centre of Fishguard at a junction with the A487. Climbing away from sea level, it follows a south-easterly course past Llanychaer to New Inn where it crosses the B4329. The B4313 then skirts Goetty Mountain to reach the village of Maenclochog.
From here it continues southeastwards through rural Pembrokeshire, descending in undulating fashion to the Eastern Cleddau River, which it crosses by means of Llandre Bridge. After passing beneath the Whitland to Clarbeston Road section of the Carmarthen to Fishguard and Milford Haven railway, the road passes through the small village of Bethesda before crossing the A40 at a staggered junction (Redstone Cross) and terminating 1.5 km further south on the A478 one-way system in Narberth.