Islandeady Lough (Irish: Loch Oileán Éadaí) is a freshwater lake in the west of Ireland. It is located in County Mayo.

Islandeady Lough measures about 2 km (1.2 mi) long and 1 km (0.6 mi) wide. It is located about 10 km (6 mi) west of Castlebar.

Islandeady Lough drains to neighbouring Castlebar Lough via the Castlebar River. The river in turn flows through Lough Lannagh before passing through Castlebar. Islandeady Lough is stocked annually with brown trout.