| Rotten Island | |
| Map: | island of Ireland |
| Native Name: | An tOileán Bréan |
| Native Name Link: | Irish language |
| Location: | Atlantic Ocean |
| Coordinates: | 54.6167°N -34°W |
| Country: | Ireland |
| Country Admin Divisions Title: | Province |
| Country Admin Divisions: | Ulster |
| Country Admin Divisions Title 1: | County |
| Country Admin Divisions 1: | Donegal |
| Population: | 0 |
Rotten Island (Irish: An tOileán Bréan) is a small island close to the entrance of Killybegs Harbour, an inlet of Donegal Bay, in County Donegal, Ireland.
Rotten Island lighthouse was established in 1838 and is still operational. It has a white conical masonry tower with a red gallery and is operated by the Commissioners of Irish Lights.[1]