This article is about the Class III road numbered C313 maintained by DfI Roads. For other roads numbered C313, see C313.
The C313 runs along the southern edge of the Mourne Mountains for much of its length. Starting on the coastal A2 at Mullartown, the road climbs inland to the north west before sharply turning left and crossing the Annalong River. The road follows the southern slopes of the mountains, overlooking the low lying land to the south. Soon the north end of the N-S component of the C315 is reached and not long after that the road turns sharply to the south and TOTSOs west, with the C314 continuing down towards Kilkeel. The road then crosses Kilkeel River as it flows out of Silent Valley Reservoir and further west it ends on the B27 near the village of Attical.