This articles lists the islands of County Mayo, the mainland of which is part of the island of Ireland. Included in this list are named offshore and freshwater islands as recorded by Ordnance Survey Ireland or the Placenames Database of Ireland. Additionally, areas of ecological significance related to both offshore and freshwater islands, designated by the National Parks and Wildlife Service, are also listed.
Although County Mayo has hundreds of offshore and freshwater islands, only a handful of islands and island groups are large enough to be distinguishable on a typical map of the county, namely Achill Island, Clare Island and Inishturk, along with the island clusters of Duvillaun, Inishkea, Clew Bay and the major loughs. There are over 100 islands which are greater than in area. The largest island is Achill, which extends to , making it Ireland's largest offshore island.
Due to its abundance of bays, inlets and offshore islands, Mayo is reputed to have the longest coastline of any county in Ireland, at or approximately 21% of the total coastline of the State.
The geology and geomorphology of the county and its islands is among the most varied and complex in Ireland. Islands such as those at Clew Bay are low-lying, formed when rising sea levels drowned a vast field of drumlins, while others like Clare Island and Achill are characterised by mountains and towering sea-cliffs, of which Croaghaun are the third-highest in Europe, at
The bedrock geology of the islands is broadly divided into two groups. Those north of Clew Bay such as Achill and the islands off the Mullet Peninsula are generally of ancient Dalradian age, similar to County Donegal and the Grampian Highlands. Inishglora contains some of the oldest rocks in Ireland, at 1.75 billion years old. Further south, the islands are much more diverse. Clare island alone is composed of Cambrian, Ordovician, Silurian and Carboniferous terranes sutured together. Geologically, the Clew Bay islands themselves are the youngest in the county, formed during the Lower Carboniferous about 350 million years ago.
The county's offshore islands - and islands off the west coast of Ireland generally - developed their own distinct culture and traditions stretching back centuries. Records from the 1841 Census show that 47 of County Mayo's offshore islands were inhabited, with a combined population of approximately 10,000. The Great Famine resulted in widespread or total depopulation of the islands. Towards the end of the 19th century the population of the larger islands began to recover somewhat, only to be set back by emigration following independence as the Irish government initially encouraged the evacuation of the islands due to the cost of providing services to them, further hastening the decline.
Today, the islands are recognised by the State as an integral part of Ireland's national heritage, preserving the remnants of a unique aspect of Irish culture. The remaining inhabited islands receive support and funding through the Department of Culture, Heritage and the Gaeltacht. As of the 2016 Census, there are 2,700 people living on 14 of the county's offshore islands (of which 2,440 live on Achill), accounting for 1.87% of the county's population.
Islands of Mayo by population Demographics The 2016 census records 14 offshore islands as having a usually resident population. Achill has been connected to the mainland via bridge since 1887, making Clare Island the county's most populous unconnected island, with 159 inhabitants as of 2016. This makes Clare Island the fifth-most populous unconnected island in Ireland, after the three Aran Islands off Galway and Arranmore off County Donegal.
Mayo County Council is responsible for the governance of the islands, and islanders are entitled to certain benefits and exemptions, such as lower motor tax rates. The islands also receive funding from the Department of Culture, Heritage and the Gaeltacht, as several offshore islands along with much of northwest Mayo are recognised Gaeltacht areas.
As many as 47 offshore islands had permanent populations prior to the Great Famine. Communities had resided on these islands for generations, and their remains can still be seen to this day through the villages, stone walls and lazybeds which they left behind. By the end of the 19th century most of the county's islands had been deserted. In contrast, Achill benefitted from a bridge to the mainland which allowed the population to temporarily rebound, reaching its all-time peak in 1911.
Emigration from the islands continued into the 20th-century as traditional industries such as fishing and textiles were unable to provide an attractive, or in many cases adequate, income to young islanders. In recent times, the islands have become a popular tourist destination and depend heavily on the tourism and hospitality sector. Their population swells during the summer months, particularly on Achill and Clare. Popular activities include surfing, sailing, island-hopping in Clew Bay, spiritual retreats and eco-tourism.
The following table shows population trends for the fourteen currently inhabited islands as of the last census. The overall trend is a continuing decline in the population of Mayo's offshore islands, which is currently at a historic low. The county as a whole was one of just three in Ireland to record a population decrease between 2011 and 2016. The population of Mayo during this time decreased by 0.2%, whereas the population of the islands fell by 5.3%. Although the overall population fell during this time, four previously uninhabited islands received new residents, including Achillbeg, which had been uninhabited since 1965.
Currently inhabited islands RankIslandBaronyPopulation 2016 2011 1841 Peak Population (if not 1841) 1 Achill Burrishoole 2,440 2,569 4,901 5,260 (1911) 2 Clare Murrisk 159 168 1,615 3 Inishturk Murrisk 51 53 577 4 Inis Bigil Erris 18 25 67 162 (1926) 5 Collanmore Burrishoole 7 4 213 215 (1851) 6 Inishnakillew Burrishoole 6 7 126 7 Inishlyre Burrishoole 4 4 113 122 (1851) 8 Clynish Burrishoole 4 4 87 9 Inish Turk Beg Burrishoole 4 10 57 10 Duvillaun More Erris 2 2 31 11 Collanbeg Burrishoole 2 0 4 9 (1861) 12 Achillbeg Burrishoole 1 0 178 13 Inishkea North Burrishoole 1 0 155 14 Rosbarnagh Burrishoole 1 0 42 Total2,7002,8468,166 Change -5.3% -65.2% -
Formerly inhabited islands IslandBaronyPopulation 1841 Peak Population (if not 1841) Year Abandoned Rosmore Island Burrishoole 133 Moynish More Burrishoole 99 1881-1891 Island More Burrishoole 88 Rosturk Island Burrishoole 64 Inishkea South Erris 62 1934 Inishdaff Burrishoole 57 Inishgowla South Burrishoole 52 Inishtubbrid Burrishoole 42 Knockycahillaun Burrishoole 41 Inishcottle Burrishoole 40 45 (1911) 2011-2016 Derrinish Burrishoole 40 Inishquirk Burrishoole 37 Inisheeny Burrishoole 36 Annagh Islands Erris 33 1851 Illanataggart Burrishoole 33 Inishgort Burrishoole 32 35 (1871) 2006-2011 Crovinish Burrishoole 32 Inishoo Burrishoole 29 Bartragh Island Tirawley 28 1951 Inisherkin Burrishoole 28 Inishgowla Burrishoole 28 Inishnacross Burrishoole 27 Inishraher Burrishoole 25 Inishturlin Burrishoole 25 Inishkeel Burrishoole 23 Inishbee Burrishoole 20 Inishglora Erris 16 Eagle Island Erris 15 22 (1861) 1988 Dorinish Burrishoole 13 15 (1871) 1901 Inishbobunnan Burrishoole 13 Inishilra Burrishoole 12 Inishcooa Burrishoole 6 Barranagh Island Erris 0 1 (1874) late 1800s Blackrock Island Erris 0 15 (1881) 1974 Roman Island Burrishoole 0 36 (1911) 1966-1971 Total 1,229
Islands of Mayo by area
Larger islands With the exception of Achill, County Mayo's islands are generally small in size, with only 13 larger than and 3 larger than . There are numerous offshore islands in the 10 to 100 acre range, along with at least 15 freshwater islands larger than 10 acres, the largest of which is Illannaglashy on Lough Conn at .
The one hundred largest islands in the county are listed below. "F" designates a freshwater island.