The River Inny is a significant tributary of the River Shannon, draining a large catchment of approximately 1,278 square kilometers across Counties Cavan and Longford in Ireland's midlands. Rising upstream of Lough Sheelin in County Cavan, the river flows in a south-westerly direction before entering Lough Ree near Ballymahon, County Longford. The catchment geology is predominantly limestone, which shapes the river's character and water chemistry throughout its length. Land use is primarily agricultural, with pockets of cutaway bog scattered throughout the catchment. The Inny is notable as the eastern tributary through which roach first entered the Shannon river system, and it supports a diverse range of both game and coarse fish species. Several Special Areas of Conservation (SACs) exist within the catchment, including the Moneybeg and Clareland Bogs SAC, Garriskil Bog SAC in the upper reaches, and Lough Ree SAC at the lower end where the river meets the Shannon system.