The River Moy (Abhainn na Muaidhe in Irish) rises in the Ox Mountains in County Sligo in the northwest of Ireland. For the greater part of its length the Moy flows southwestward, entering County Mayo and passing not far from Swinford before turning north near the village of Kilmore and heading for the historic town of Ballina, where it empties into Killala Bay and the Atlantic Ocean.

The river is noted as one of the best salmon fisheries in Europe, and the beautiful Moy valley, with its ancient churches and abbeys, is a prominent tourist destination.