kingdom · British Isles

East Breifne

1256 CE – 1607 CE (approx.) · capital Cavan

The O'Reilly lordship of County Cavan, a Gaelic state with a town at Cavan whose 'O'Reilly money' circulated in the Pale, until the Plantation of Ulster.

Origins

East Breifne emerged when the Kingdom of Breifne split in 1256 and the O'Reillys, Muintir Mhaoilmhordha, took the eastern part. They founded the town of Cavan beside their castle on Tullymongan hill and a Franciscan friary, and also held the island fortress of Clough Oughter.

Rule and society

The O'Reillys traded with the Pale, and their 'O'Reilly money', clipped coins circulating in the 15th century, was common enough to be banned by the Irish Parliament in 1447. The lordship was organised in Gaelic fashion, with tanistry, brehon law and a hereditary learned class.

Decline and legacy

Under the Tudors the area became County Cavan in 1584. After the Nine Years' War and the Flight of the Earls it was included in the Plantation of Ulster from 1609, with lands granted to English and Scottish settlers.

Lineage

Kingdom of Breifne 700 CE – 1256 CEEast BreifneKingdom of Ireland 1542 CE – 1800 CE

More states of British Isles →

Cite this page
APA
The Epoch Institute. (2026). East Breifne. In The Epoch Institute States Register. https://the-epoch-institute.org/state/east-breifne
MLA
“East Breifne.” The Epoch Institute States Register, The Epoch Institute, 2026, https://the-epoch-institute.org/state/east-breifne. Accessed .
Chicago
The Epoch Institute. “East Breifne.” The Epoch Institute States Register. 2026. https://the-epoch-institute.org/state/east-breifne.
Harvard
The Epoch Institute (2026) ‘East Breifne’, The Epoch Institute States Register. Available at: https://the-epoch-institute.org/state/east-breifne (Accessed: ).

Last reviewed October 2026Random state ↻