The Kingdom of Breifne or Bréifne ([ˈbrʲeːfnʲe]; anglicized Breffni, Breffny, Brefnie, Brenny) was a confederation of Irish túaithe headed by a ruirí drawn from 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.