Erris is a barony in northwestern County Mayo in Ireland consisting of over 230,452 acres (932.61 km2), much of which is mountainous blanket bog.

Parts of Erris are in a Gaeltacht area, with first-language speakers of Irish in the following areas of the barony: An Fál Mór, Tamhaiin na hUltaí, Glais, Eachléim, Tearmann, Tránn, An Mullach Rua, Cartúr, An Baile Úr, Cill Ghallagáin, An Corrán Buí, Ceathrú na gCloch, Port a' Chluaidh, Ros Dumhach and Ceathrú Thaidhg.

Erris has a large range of habitats including blanket bogs, estuaries, salt marshes, fresh water lakes, coasts, cliffs, machair, sand dunes, sandy beaches and rocky shores.

Brent geese overwinter here feeding along the estuaries,[6] and corncrake, chough, rock dove and twite are sometimes seen at Erris Head.

[8] Pink or orange striped gneisses are found along the beaches of Elly Bay and Annagh Head where they have become separated from the same rocks on the east coast of Northern Canada over hundreds of millions of years by the separation of tectonic plates in the mid Atlantic Ocean.

[12] The coastline of Erris has some of "the grandest sea cliffs in Ireland"[13] over the Atlantic Ocean from where the next stop is the east coast of America.

[19] With minor changes in climate and high rainfall levels the land became blanketed by the bog and remains that way to the current day.

Oliver Cromwell's policy (mid 17th century) of sending the native Irish who refused to bow down to him "to hell or to Connaught" saw a large influx of population into Erris where the disinherited native Irish tried to eke a living from very poor quality agricultural land under the tenancy of the landlords and their agents.

[citation needed] During the Irish Famine of 1845 - '47 many died in Erris despite the close proximity of the sea, because they could not raise the cash to fund a passage to America.

[21] The Ulster Cycle legend of the Táin Bó Flidhais concerns the Barony of Erris in the time period of approx the 1st century AD.

The children were turned into swans by their jealous stepmother and doomed to spend the next 900 years on lakes and waters in Ireland.

Táin Bó Flidhais is the tale of a cattle raid in which raiders came to Erris from the Royal site at Cruachán (Rathcroghan) at Tulsk, County Roscommon to Rathmorgan Fort (Iorras Domhnann) at the south end of Carrowmore Lake in the centre of the Barony.

[28][29] In 1993, the Tír Sáile Sculpture Trail project was carried out to commemorate 5,000 years of habitation in County Mayo.

The creation of the sculpture trail took the form of the Meitheal, a traditional method of working where a group of workers come together to achieve a common objective.

Raw, unodourised natural gas from fields under the Atlantic Ocean is planned to be piped at high pressure at Glengad and through the townlands of Kilcommon, to a refinery 10 km inland.