County Offaly (Irish Gaelic: Uíbh Fhailí) is a county in the Republic of Ireland, bordered by County Laois, County Galway, County Kildare, County Meath, County Roscommon, County Tipperary and County Westmeath. It was formed during the reign of Mary I of England as King's County, named for Phillip II of Spain.

The southern part of the county is occupied by the Slieve Bloom Mountains, the northwestern part is the floodplain of the River Shannon and the remainder consists of large bogs including the Bog of Allen and Boora Bog.

The main town in the county is Tullamore, while smaller settlements include:

Banagher, Birr
Cadamstown, Clara, Clonmacnois
Daingean
Edenderry
Ferbane
Kinnitby, Kilcormac
Shannonbridge, Shannon Harbour