[6][7] The Colligan River rises in the Monavullagh Mountains, flows southwards under the Scart Bridge, passes under the N72 at Kildangan, and then turns eastwards into a wide estuary at Dungarvan.

It is bridged by the N25 (The Bypass) and R911 (The Causeway) before entering the Celtic Sea.

The Colligan River is a noted salmon and trout fishery.

[10] Colligan gives its name to a civil parish northeast of Dungarvan in the barony of Decies-without-Drum.

[11] There was formerly a roughly coterminous Catholic parish in the Diocese of Waterford and Lismore,[12] which gave its name to Colligan–Emmets GAA club.