| Conventional Long Name: | Fermanagh |
| Common Name: | Fermanagh |
| Year Start: | 10th century |
| Year End: | 1607 |
| Status Text: | Túatha of Airgíalla |
| P1: | Airgíalla |
| S1: | County Fermanagh |
| Flag S1: | Ferm arms.png |
| Border S1: | no |
| S2: | Kingdom of Ireland |
| Flag S2: | Arms of Ireland (Historical).svg |
| Border S2: | no |
| Image Map Caption: | Fermanagh in the 15th–16th centuries |
| Today: | United Kingdom of Great Britain and Northern Ireland |
| Capital: | Lisnaskea[1] |
| Common Languages: | Irish |
| Government Type: | Elective monarchy |
| Title Leader: | King / Chief |
| Leader1: | Cathal Ó Dubhdara |
| Year Leader1: | d.1009 |
| Leader2: | Cú Chonnacht Óg Mag Uidhir (last; half-brother of Hugh Maguire)[2] |
| Year Leader2: | 1600–1607 |
Historically, Fermanagh (Irish: Fir Manach), as opposed to the modern County Fermanagh, was a kingdom of Gaelic Ireland, associated geographically with present-day County Fermanagh. Fir Manach originally referred to a distinct kin group of alleged Laigin origins. The kingdom of Fermanagh was formed in the 10th century, out of the larger kingdom of Uí Chremthainn, which was part of the overkingdom of Airgíalla.[3] By the late 11th century it had grown to cover all of what is now County Fermanagh.[3] The kingdom came to be ruled by the Mag Uidhir (Maguire) clan from the late 13th century onward. They were based at Lisnaskea, and their royal inauguration site was nearby Sgiath Gabhra (Skeagoura), now called Cornashee.[4] Under Hugh Maguire, Fermanagh was involved in the Nine Years' War against English rule. His successor, Cú Chonnacht Óg Mag Uidhir, was one of the Gaelic Irish leaders who fled Ireland during the Flight of the Earls. Fermanagh was subsequently merged into the Kingdom of Ireland as County Fermanagh.
The original Fir Manach or Fear Manach, that is to say the Manach or Monaigh people in the north of Ireland, claimed descent from the Laighin of Leinster.[5] They reached upper Lough Erne in ancient times. According to the Book of Glendalough (also known as the Rawlinson B 502) a genealogy is provided for the early Manach people and they claim descent from Dáire Barrach, the son of Cathair Mór, High King of Ireland.[5] Dáire Barrach's descendants elsewhere in Ireland are today known as the MacGorman (Mac Gormáin) and ruled Uí Bairrche during the Middle Ages. Cathair Mór himself had ruled Ireland as King of Tara in the 2nd century.
The geopolitical situation in Ireland changed during the 4th and 5th centuries, owing to the rise of the descendants of Conn of the Hundred Battles. Most significantly for the Fir Manach, the kingdoms of Airgíalla (under the descendants of the Three Collas), the kingdom of Ailech (under the Uí Néill) and the kingdom of Connacht (under the Uí Briúin) arose. According to Peadar Livingstone, the territory of Fermanagh became disputed between these groups and the previously ruling Fir Manach people.[6]
By the end of the 11th century, Fermanagh had decisively re-emerged as a sovereign kingdom in the region. The rulers of this kingdom were drawn from the Airgíalla. Early on the territory drew kings from three branches of Clann Lugainn; the Ó hEignigh (O'Heany), Maolruanaidh (Mulrooney) and Ó Dubhdara (Darragh). These families claimed descent from the Three Collas, in the person of Colla Fochríth and were thus kinsmen of the MacMahon kings of Airgíalla. Towards the end of the 13th century, the Mag Uidhir (Maguire) arose to the kingship of Fermanagh and with the exception of some challenges from the Ó Domhnaill of Tyrconnell, this would remain the situation until the end of the kingdom in 1607 with the Flight of the Earls.
See main article: Kings of Fermanagh. The Annals of the Four Masters mention the following as Kings of Fermanagh (Irish: Fir Manach).[7]