This article is about the Class III road numbered C684 maintained by DfI Roads. For other roads numbered C684, see C684.
The C684 is the former alignment of the A4 west of Dungannon. Starting in Dungannon, the road heads west from a roundabout on the A45 and soon leaves the town. The road meanders its way past Eskragh Lough, keeping south of Castlecaulfield. The road ends where it meets the B34 which is itself a former alignment of the A4, with the modern A4 dual carriageway located a little further south.