County Sligo (Irish: Contae Shligigh) is a county in Ireland. It is located in the Border Region and is also part of the province of Connacht. It is named after the town of Sligo.
The county was theoretically formed in 1585, but was not made a reality until after the chaos of the Nine Years' War had ended, in 1603. Its boundaries reflect the Ó Conchobhair Sligigh overlordship of Lower Connacht (Irish: Íochtar Connacht) as it was at the time of the Elizabethan conquest.
The megalithic cemetery of Carrowmore is located in County Sligo. It forms part of a huge complex of Stone Age remains connecting Carrowkeel in south Sligo to the Ox Mountains, to the Cuil Irra Peninsula, where Queen Maeve's tomb dominates the western skyline from the crest of Knocknarea Mountain.