Connacht, province in northwestern Ireland. It includes the counties of Galway, Leitrim, Mayo, Roscommon, and Sligo. The western coast of the province, on the Atlantic Ocean, is broken by many bays and is fringed with islands. The interior, especially the western half, is mountainous and rugged, forming picturesque scenery. Although Connacht is the least fertile of the four provinces of the country, farming and sheep raising are the principal occupations. Fishing is also important.

In ancient times, the province was a pre-Celtic domain. Gaelic rule was established about AD150, and Connacht became one of the Irish kingdoms. Its rulers were the O'Connors, the most notable of whom was Turloch O'Connor. The O'Connors were almost exterminated at the Battle of Athenry, fought against the English in 1316; in the 15th century the title to Connacht passed to the English crown. In 1590 Connacht was divided into six counties, one of which, county Clare, was later placed within the province of Munster. Area, 17,122 sq km (6611 sq mi); population (1991) 423,031.