County Fermanagh in the context of "Counties of Northern Ireland"

The Plantation of Ulster (Irish: Plandáil Uladh; Ulster Scots: Plantin o Ulstèr) was the organised colonisation (plantation) of Ulster – a province of Ireland – by people from Great Britain during the reign of King James VI and I.

Small privately funded plantations by wealthy landowners began in 1606, while the official plantation began in 1609. Most of the land had been confiscated from the native Gaelic chiefs, several of whom had fled Ireland for mainland Europe in 1607 following the Nine Years' War against English rule. The official plantation comprised an estimated half a million acres (2,000 km) of arable land in counties Armagh, Cavan, Fermanagh, Tyrone, Donegal, and Londonderry. Land in counties Antrim, Down, and Monaghan was privately colonised with the king's support.

Lough Erne (/lɒx ɜːrn/ LOKH URN, from Irish Loch Éirne) is two connected lakes in County Fermanagh, Northern Ireland. It is the second-largest lake system in Northern Ireland and Ulster, and the fourth largest in Ireland. The lakes are widened sections of the River Erne, which flows north and then curves west into the Atlantic. The smaller southern lake is called the Upper Lough as it is higher up the river. The larger northern lake is called the Lower Lough or Broad Lough. The town of Enniskillen lies on the short stretch of river between the lakes. The lake has more than 150 islands, along with many coves and inlets. The River Erne is 80 miles (129 km) long and drains an area of about 1,680 square miles (4,350 km).

Enniskillen (/ˌɛnɪsˈkɪlən/ EN-iss-KIL-ən, from Irish: Inis Ceithleann [ˈɪnʲɪʃ ˈcɛlʲən̪ˠ], 'Ceithlenn's island') is the largest town in County Fermanagh, Northern Ireland. It is in the middle of the county, between the Upper and Lower sections of Lough Erne. It had a population of 14,086 at the 2021 census. Enniskillen Castle was built in the 15th century as a stronghold of the Maguires, before coming under English control in the early 17th century. The castle and town were expanded during the Plantation of Ulster. It was the seat of local government for the former Fermanagh District Council, and is the county town of Fermanagh. The town is in a civil parish of the same name.

Tyrconnell (Irish: Tír Chonaill, meaning 'Land of Conall'), also spelled Tirconnell and Tirconaill, was a kingdom of Gaelic Ireland. It is associated geographically with present-day County Donegal, which was officially named County Tirconaill between 1922 and 1927. At times it also included parts of County Fermanagh, County Sligo, County Leitrim, County Tyrone and County Londonderry at its greatest extent. The kingdom represented the core homeland of the Cenél Conaill people of the Northern Uí Néill and although they ruled, there were smaller groups of other Gaels in the area.

From the 5th century founding of Cenél Conaill, the tuatha was a sub-unit of the larger kingdom of Ailech, along with their Cenél nEógain cousins, fellow descendants of Niall of the Nine Hostages. Their initial ascent had coincided with the decline of the Ulaid, whose kingdom of Ulster receded to the north-east coast. In the 12th century the kingdom of Ailech split into two sovereign territories and Cenél Conaill became Tír Chonaill under the Ó Domhnaill (O'Donnell) clan. It was the location of fighting during the Nine Years' War (Ireland) at the end of the 16th century. It continued to exist until the 17th century when it was incorporated into the English-ruled Kingdom of Ireland following the Flight of the Earls.

Cavan (/ˈkævən/ KAV-ən; Irish: An Cabhán, meaning 'the hollow') is the county town of County Cavan in Ireland. The town lies in Ulster, near the border with County Fermanagh in Northern Ireland. The town is bypassed by the main N3 road that links Dublin (to the south) with Enniskillen, Ballyshannon and Donegal Town (to the north).

Airgíalla (Old Irish pronunciation: [ˈœɾʲɣʲiːa̯l̪a]; Modern Irish: Oirialla, English: Oriel, Latin: Ergallia) was a medieval Irish over-kingdom and the collective name for the confederation of tribes that formed it. The confederation consisted of nine minor kingdoms, all independent of each other but paying nominal suzerainty to an overking, usually from the most powerful dynasty. Airgíalla at its peak roughly matched the modern dioceses of Armagh and Clogher, spanning parts of counties Armagh, Monaghan, Louth, Fermanagh, Tyrone and Londonderry. Its main towns were Armagh and Clogher. The name's usage survives as a cultural area of folk tradition in South East Ulster and adjoining areas of County Louth.

According to legend, Airgíalla was founded by the Three Collas, who are said to have conquered what is now central Ulster from the Ulaid. The decisive victory was the battle of Achadh Leithdheirg, said to have been fought around the year 331. However, this tale is thought to be mostly fiction, and the actual year and circumstances of how the Airgíalla confederation came about is unknown.