County Louth is a coastal county in the Eastern and Midland Region of Ireland, within the province of Leinster. Louth is bordered by the counties of Meath to the south, Monaghan to the west, Armagh to the north and Down to the north-east, across Carlingford Lough. It is the smallest county in Ireland by land area and the 17th most populous, with just over 139,100 residents as of 2022. The county is named after the village of Louth. Louth County Council is the local authority for the county.

There are four provinces of Ireland: Connacht, Leinster, Munster and Ulster. The Irish word for this territorial division, cúige, meaning "fifth part", suggests that there were once five, and at times Meath has been considered to be the fifth province. In the medieval period, however, there were often more than five. The number of provinces and their delimitation fluctuated until 1610, when they were permanently set by the English administration of James I. The provinces of Ireland no longer serve administrative or political purposes but function as historical and cultural entities.