The River Inny (Irish: An Eithne) is a tributary of the River Shannon, rising near Oldcastle in County Meath and flowing approximately 88.5 kilometres through a series of lakes before entering Lough Ree at Inny Bay. Its name derives from the mythological figure Ethniu or Eithne, who reputedly died in rapids in the river's lower reaches. The river runs largely over limestone and passes through counties Longford and Westmeath, forming the county boundary for portions of its lower course.

For paddlers, the most popular section runs from Newcastle Bridge to Ballymahon Bridge, a distance of roughly 4 kilometres and rated Grade 2–3. This stretch is widely regarded as one of the more accessible moving-water runs in Ireland, owing to its central location and straightforward put-in. The Newcastle Bridge car park offers ample parking and a concrete slipway with steps. The character of this section is primarily briskly moving flatwater interspersed with numerous short rapids, many of which contain pour-overs, holes, stoppers, and small waves suitable for skill practice. The rapids are generally considered safe and navigable for paddlers being introduced to moving water.

Downstream of Ballymahon Bridge, a notable feature forms at higher water levels: a wave-hole near the Meat Factory that stretches nearly the full width of the river. This wave is described as retentive enough for extended surfing while still flushing paddlers out if they lose control, making it suitable for freestyle practice. The primary hazard on this section is a stand of trees located below the Meat Factory Hole; all other drops are considered safe. A useful water level indicator is the bridge in Ballymahon town — visible small waves suggest the river is worth paddling, while a covered ledge on the bridge indicates the Meat Factory wave is at an optimal level.

A longer multi-day route is also possible, starting from Finea and travelling the full length of the river to the Shannon over several days, passing through Lough Derravaragh and stopping at Abbeyshrule, where a slipway on river left provides access a short distance past the bridge. The Rustic Inn in Abbeyshrule is noted as a local food option. Landowner access at Shrule Bridge is provided by a private field owner who has installed a stile and bins; paddlers are asked to respect this arrangement by leaving no litter.