Connacht (Connachta) contains the present-day counties of Mayo, Sligo, Leitrim, Roscommon, and Galway. The influence of Connacht's kings and of later Norman lords has left this the most Gaelic and Norman part of Ireland. Situated in the northwest, the area is 17,120 sq km (6,610 sq mi).

In ancient times, the province was a pre-Celtic domain. Gaelic rule was established about AD 150, and Connaught became one of the five 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 and fought against the English in 1316.

The ancient capital was Cr�achu (Cr�achan, present day Rathcroghan in Co. Roscommon). A few of the legendary persons or groups associated with this province are King Ailill and Queen Medb, and Findabair (Gwenivere), who was the daughter of Ailill and Medb. Near present-day Sligo Town is Knocknarea (the legendary burial place of Medb), Benbulben, and Drumkill. In the Ulster Cycle, Connacht is the enemy of the Ulaid, but this may obscure the probable historical conflict between Mide under the U� N�ill and Ulaid. Medb is said to be the daughter of the king of Temuir.

In the 15th century the title to Connaught passed to the English crown. In 1590 Connaught was divided into six counties, one of which, county Clare, was later placed within the province of Munster.