County Offaly (Irish: Contae Uíbh Fhailí) is a county in Ireland. It is part of the Midlands Region and is also located in the province of Leinster. It is named after the ancient Kingdom of Uí Failghe and was formerly known as King's County. Offaly County Council is the local authority for the county. The population of the county is 78,003 according to the 2016 census.

Offaly is the 18th largest of Ireland's 32 counties by area and the 24th largest in terms of population. It is the fifth largest of Leinster's 12 counties by size and the 10th largest by population. It is the largest county by area and the third largest by population in the Midlands.

Tullamore is the county town and largest town in Offaly and is the 30th largest in Ireland. Offaly borders seven counties: Galway, Roscommon, Tipperary, Laois, Westmeath, Kildare and Meath. The Slieve Bloom Mountains are in the southern part of the county on the border with County Laois. Offaly has the 24th highest county peak in Ireland. The highest point is Arderin (Irish: Ard Éireann) in the Slieve Blooms at 527 metres (1,729 feet). The Slieve Bloom Mountains contain the county's highest points including Stillbrook Hill and Wolftrap Mountain which are the county's second and third highest peaks. Croghan Hill rises from the Bog of Allen and is located in northern Offaly. Although only 234 metres high, it is known for its view over the surrounding area and it stands out by itself.

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