The Gaddagh is a 5-kilometre whitewater river in County Kerry, Munster, rated Grade 4–5. Its headwaters originate in Lochs Callii and Gabhracht on the north side of the Macgillycuddy Reeks mountain range, at an elevation of approximately 450 metres. The river flows through Hags Glen and down the Carrauntoohil Valley before joining the River Leaune, which eventually discharges into the sea at Killorglin.

The river is divided into three distinct sections. The top section, above the waterfalls or "drops" in Hags Glen, is considered potentially Grade 5. The middle section, from below the drops to a point below Cronin's Yard, is generally regarded as Grade 4. The final wooded section, from Cronin's Yard to Gaddagh Bridge, is Grade 3, where the river has widened, its gradient has reduced, and the intensity of flow has diminished. Throughout the upper sections, the river has cut a series of terraces through the mountain over time, producing a number of waterfalls.

The put-in is above Hags Glen, above the series of waterfalls, and the take-out is at Gaddagh Bridge. The river maintains a steep gradient for the majority of its transit through Hags Glen, which is a defining characteristic of the paddling experience.

A critical planning consideration is that the Gaddagh is highly dependent on rainfall and runs only sporadically. Continuous heavy rain is required to bring the river to a paddleable level, typically supplied by slow-moving low-pressure weather fronts approaching from the west. The height and profile of the surrounding mountains cause orographic uplift, which enhances rainfall and causes river levels to rise rapidly. Because flooding is both infrequent and short-lived, it is generally not possible to plan a trip in advance; decisions to paddle are typically made at short notice by groups already in the area. Any paddler considering this river should be prepared to act opportunistically when conditions align.