Sligo ('abounding in shells') is a coastal seaport and the county town of County Sligo, Ireland, within the western province of Connacht. With a population of approximately 20,000 in 2016, it is the second largest urban centre in the West of Ireland, with only Galway being larger. The Sligo Borough District constitutes 61% (38,581) of the county's population of 63,000.

Sligo is a historic, cultural, commercial, industrial, retail and service centre of regional importance in the West of Ireland, and is served by rail, port and road links. Sligo is also a tourist destination, being situated on the Wild Atlantic Way, with many literary and cultural associations.

Situated on a coastal plain facing the Atlantic Ocean, Sligo is located on low gravel hills on the banks of the Garavogue River between Lough Gill and the estuary of the Garavogue river leading to Sligo Bay. The town is surrounded on three sides by an arc of mountains, with the Ox Mountain ridges of Slieve Daeane and Killery Mountain to the southeast bordering Lough Gill. The flat topped limestone plateaux of Cope's, Keelogyboy and Castlegal Mountains to the north and northeast and the singular hill of Knocknarea with its Neolithic cairn to the west and the distinctive high plateau of Benbulben to the north.

Sligo is an important bridging point on the main north/south route between Ulster and Connacht. It is the county town of County Sligo and is in the Barony of Carbury (formerly the Gaelic tuath of Cairbre Drom Cliabh). Sligo is the diocesan seat of the Roman Catholic Diocese of Elphin. It is in the Church of Ireland Diocese of Kilmore, Elphin and Ardagh.

County Sligo is one of the counties of the province of Connacht. It is part of the Border Region, a region of over 500,000 people which also comprises the counties of Cavan, Donegal, Leitrim, Louth and Monaghan.