Kingdom of Breifne

The Kingdom of Breifne or Bréifne ([ˈbrʲeːfnʲe]; anglicized Breffny, Brefnie, Brenny) was the traditional territory for an early Irish tribal group known as the Uí Briúin Bréifne. The Bréifne territory included current day Irish counties of Leitrim and Cavan, along with parts of County Sligo (an area roughly equivalent to the modern Roman Catholic Diocese of Kilmore).

Breifne is said to derive from an obsolete Irish word meaning 'hilly', a description which describes the topography of this part of Ireland. It was referred to as the rough third of Connacht.

Alternatively, the Metrical Dindshenchas states the name is derived from Brefne, daughter of Beoan mac Bethaig, a brave soldier-woman.

At its height in the 12th century, when Tigernán Ua Ruairc was king of Bréifne, it extended from Kells in County Meath to Drumcliffe in County Sligo.

In 1296, according to the Annals of the Four Masters "Maelpeter O'Duigennan, Archdeacon of Breifny...died."

In 1256, a great battle was fought between the O'Rourkes and the O'Reillys near Ballinamore. This led to the division of Breifne between the O'Rourkes and O'Reillys. The Bréifne region was split into East Bréifne and West Bréifne.