This article is about the Class III road numbered C66 maintained by DfI Roads.
For other roads numbered C66, see C66
The C66 is a lengthy route in County Antrim which starts on the B97 in the upper reaches of Glenarm. The road initially heads south west through the hilly landscape, passing the northern terminus of the C70 as it does so, before turning round west and north west. Before long the road encounters a tight bend after which it heads in a westward direction to continue up and over hills. There is a spur forming part of the C66 which links to the C67 in nearby Buckna along this section. The road soon negotiates two TOTSOs, turning south on the first and west on the second which turns it away from the beginning of the C65. For the remainder of its route the C66 heads south west across the B94 at a crossroads before coming to an end on the C64, three kilometres short of Ballymena.