The Cladagh River (from Irish an Chlaideach 'washing river') is a small river in County Fermanagh, formed from three rivers and a number of streams draining off the northern slopes of Cuilcagh mountain, which combine underground in the Marble Arch Cave system. On the surface, the River Cladagh emerges from one of the largest karst resurgences in the UK, before flowing through Cladagh Glen Nature Reserve and eventually draining into the Arney River.