Rotten Island – Killybegs harbour light

Overview

Rotten Island Lighthouse sits on a small, wind-swept rock at the south-east corner of the entrance to Killybegs Harbour in County Donegal. Built between 1837 and 1838, the freestanding two-stage tower is finely cut ashlar granite painted white, a clear landmark against the Atlantic sky. Run by the Commissioners of Irish Lights, it still works as a harbour light, marking the safe passage from St John’s Point to the inner channel and anchorage.

The lighthouse is not open for interior tours, but its silhouette is easy to take in from the water on local boat trips, from the Killybegs waterfront, or from the surrounding cliffs. Its historic fabric, robust boundary walls and the story of its building make it a worthwhile stop on a Donegal coastal run.

Name and origins

The island’s Irish name is An tOileán Bréan, with the lighthouse formally Teach Solais An tOileán Bréan. Early English records anglicised this to ‘Rotten Island’. Local lore has offered various explanations over the years, but the name mostly reflects the rock’s rugged character and its role as a solitary outpost in one of Ireland’s busiest fishing ports.

History and construction

The need for a navigational aid at the harbour entrance was first raised in April 1832. Mr Drury, the Inspecting Commander of the Coastguard, initially recommended Drumanoo Point, but George Halpin, Inspector to the Ballast Board, argued that Rotten Island was the better site. The Board approved the scheme in November 1833, with statutory sanction from Trinity House shortly after.

Halpin designed both the lighthouse and the keeper’s dwellings, and the Board’s own workmen carried out the build under his direct supervision. The tapering circular tower, in cut granite, came in at about £8,850, a substantial sum for the time. The work was not without tragedy: on 15 September 1836, three workers drowned when their boat capsized returning from the rock.

The light was first shown on 1 September 1838, before the station was fully finished. It used a fixed white catoptric third-order lens, 66 feet above high water and visible for 12 nautical miles. The technology changed over the decades:

• 1910: upgraded to a fifth-order dioptric lens, flashing once every three seconds.
• 1959: the station was automated, the dioptric lens and paraffin burner replaced by a fourth-order cylindric refractor on dissolved acetylene.
• 1963: electricity was brought across the channel on an overhead cable, lifting the candlepower to 13,000 (white) and 2,600 (red sector).
• 1965: the flashing character was changed to one flash every four seconds, still in use today.

The lighthouse and its ancillary buildings are recorded on the Buildings of Ireland database as a protected structure of architectural, social and technical interest.

Viewing the lighthouse

You cannot step inside the tower, but there are good ways to see it from Killybegs:

• Coastal viewpoints – the headlands around Carntullagh Head and the Killybegs waterfront give clear sightlines. Photographers tend to go at dawn or dusk for the white tower against the dark granite shore and shifting Atlantic light.
• Boat trips – local operators in Killybegs Harbour run seasonal sightseeing cruises through the inner channel, usually passing close to the island for views of the lantern, the metal walkway and the rubble-stone boundary wall.
• Wildlife – the island’s isolation makes it a resting point for seabirds, and on calm mornings you can often spot gulls, razorbills and seals hauled out on the nearby rocks.
• Maritime heritage walks – a stroll through the historic harbour gives the context for the lighthouse’s near two centuries protecting Ireland’s largest fishing fleet.

For the technically minded, the current specifications:

Practical information

• Access – the island is uninhabited and the lighthouse strictly operational. There are no public footpaths or regular ferries to the rock, so all viewing is from the mainland or licensed commercial vessels.
• Parking – free parking in the Killybegs harbour and town centre areas, though spaces fill quickly in peak summer, so come early.
• Getting there – Bus Éireann and Local Link services connect Donegal Town and Letterkenny with Killybegs, with the bus stop a short walk from the harbour quayside where boat operators board passengers.
• Booking boat tours – seasonal cruises generally run from May to October. Operators vary, so check local listings or the harbour-side tour desks to confirm schedules and weather-dependent departures.
• Safety – the waters around Rotten Island are exposed to Atlantic swells and strong tidal currents. Follow the advice of licensed boat captains and check the marine forecast before heading out.

Nearby

• Arranmore Island – a ferry trip to Ireland’s largest offshore island, with its own historic lighthouse, coastal trails and an island community. (Arranmore)
• Killybegs Maritime & Heritage Centre – in the town centre, covering the region’s fishing industry and the Donegal hand-knotted carpet trade.
• Slieve League – a short drive west, sea cliffs rising to 596 metres, among the highest in Europe. (Ireland’s Majestic Cliffs)
• St John’s Point Lighthouse – on the opposite side of the harbour entrance, the smaller beacon that completes the pair guiding vessels into Killybegs.

Rotten Island Lighthouse is still an active aid to navigation, quietly keeping one of Ireland’s most important fishing harbours safe. Aim for a clear, calm day for the best views from the water, and check the tide tables if you want to photograph the rock at low water.