East Breifne
historic kingdom of Ireland
The Kingdom of East Breifne or Breifne O'Reilly (Old Irish: Muintir-Maelmordha; Irish: Bréifne Uí Raghallaigh, IPA: [ˈbʲɾʲeːfʲnʲə iː ˈɾˠəil̪ˠiː]) was an historic kingdom of Ireland roughly corresponding to County Cavan that existed from 1256 to 1607. It took its present boundaries in 1579 when East Breifne was renamed Cavan, after Cavan town, and shired into Ulster.
Originally part of the older Kingdom of Breifne, East Breifne emerged following a protracted war between the ruling O'Rourke clan and the ascendant O'Reillys, culminating in the kingdom's division in 1256. The Kingdom was ruled by the Ó Raghallaigh (O'Reilly) dynasty and lasted until the early 17th century.
Origins and etymology
The area of modern-day east County Cavan has been inhabited for over 5,000 years. The O'Reilly are descendant from a kin-group known as Uí Briúin, who settled the east Breifne area in the eighth century AD. At some point they splintered off from the Uí Briúin sept and became known as Muintir-Maelmordha, named after their chief Maelmordha who lived in the 9th century. They did not assume a surname until the early 11th century when they became known as O Raghallaigh, from the chieftain Raghallach. They are believed to have arrived in what is now County Cavan in the 10th century. Muintir-Maelmordha first appear in the Irish annals as a clan ruling a small territory around Lough Ramor called Machaire Gailenga in 1126, at which point they are a vassal of the O'Rourkes.
Kingdom of Breifne c.
“East Breifne” enters the record as historic kingdom of Ireland. Crown Archives preserves that source wording while asking what East, Breifne and historic can confirm, complicate or overturn.
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Vocabulary and entity names are the principal evidence signals here, because they determine the precision of every later search. The source revision retrieved here is dated Apr 1, 2026. The linked authority identifier is Q5327935. Authority coordinates are 53.917, -7.250. 1 of 2 selected statements include explicit references; 1 carry qualifiers and 0 use preferred rank. The first chronological checks are 1256, 1607, 1579 and 1126.
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This entry incorporates text from “East Breifne” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.