The River Moy is a river in the northwest of Ireland. The Moy rises at the foot of the Ox Mountains in County Sligo. It flows for 110 kilometres . For the greater part of its length, it flows southwestward, entering County Mayo and passing near Swinford before passing through Foxford then turning north near the village of Kilmore and heading for the town of Ballina, where it enters the Atlantic Ocean at Killala Bay. The Moy Estuary is eight kilometres long beginning at Ballina and running into Killala Bay. The catchment area of the River Moy is 2,086 km2.
The Moy valley, with its ancient churches and abbeys, is a prominent tourist destination.
