The Colligan River (Irish: Abhainn Choilligeáin) is a fast-flowing spate river in County Waterford, rising in the Monavullagh Mountains and flowing approximately 24 km southward before turning east into a wide estuary at Dungarvan, where it meets the Celtic Sea. With a drainage basin of 108 km² and an average discharge of 33.1 m³/s, it is reputed to be one of the fastest-flowing rivers in Europe.

The primary paddling interest is the Colligan Gorge, a tight, rocky channel running through Colligan Wood approximately 4 km north of Dungarvan town. The main whitewater run covers around 9.5 km beginning near Lackandarra Bridge and is graded 3–4, suited to intermediate and advanced paddlers. The gorge section itself is considerably shorter — around 500 m — and consists of a series of closely spaced drops in four sections, with the final drop measuring approximately 6 feet. A well-known feature called Salmon Leap is among the five distinct drops within the gorge. Paddlers wishing to lap the gorge section must carry their boats back to the start.

As a spate river, the Colligan rises and falls quickly and requires recent rainfall to be in condition. There is no longer a permanent flow gauge at the main access bridge, so checking recent reports on Irish whitewater forums or local social media groups before launching is essential. Hazards include fallen trees and seasonal electric fencing that can affect bank access; a check with local paddlers or nearby accommodation is advisable, particularly on wet weekends.

The river runs through Colligan Wood, a mixed woodland managed by Coillte featuring oak, ash, beech, and hazel. The gorge setting gives the run a distinctly enclosed, technical character. The surrounding woodland also offers two waymarked walking loops — the Inchadrisla Loop and the longer Greenane Loop (6 km) — which follow the river valley and may be of interest when water levels are unsuitable for paddling. The river is also a noted salmon and trout fishery, so paddlers should be aware of potential interactions with anglers along the banks.