County Mayo is a region on the west coast of Ireland.

Its name comes from the Irish words "Maigh Eo" meaning "Plain of the yew trees" and originates from the village of Mayo nowadays known as Mayo Abbey.

The total area is 5.586 km2.

It belongs to the Province of Connaght.

It borders on the north with the Atlantic Ocean, on the south with County Galway, on the east with County Roscommon, while the northeast is adjacent to County Sligo.

The population is 130.425 according to the 2016 census.

The largest towns in the county are Castlebar (county town) with a population of 10.852, Ballina 11.086, Westport 6063 and Claremorris with 3412.

The Mayo coat of arms consists of nine yew trees, a Patriarchal Cross and three Passion Crosses and a ship between waves.

The nine yew trees represent the nine historical baronies, four in the northern area (Erris, Burrishoole, Gallon, Tyrawley) and five in the south of the country (Claremorris, Costello, Murrisk, Klimaine and Carra).

The Patriarchal Cross (the cross with two bars) symbolizes the Catholic Archdiocese of Tuam, while the three Passion Crosses represent the other three dioceses in Mayo: Achonry, Killala and Galway-Kilmacduagh-Kilfenora.

The ship between the waves emphasizes the fact Mayo is a maritime country, while the crown with the rose on top symbolizes the apparition of the Virgin and Saints at Knock on 21st August 1879.

The Irish motto completes the coat of arms: "Dia is Muire Linn", God and Mary be with us.