The northeastern county in Northern Ireland, lying between the River Bann and Lough Neagh in the west and the North Channel in the east.
Antrim and Co. Down, to the south, were the remnant of the old Kingdom of Ulaidh (Ulster) after the O’Neill had taken over the lands west of the Bann; they were also part of the Anglo-Norman Earldom of Ulster. Antrim, not being part of the lands confiscated after the flight of the Earls in 1607, was not included in the Plantation of Ulster in the reign of James I, but it was privately and substantially settled with Scottish Presbyterians, making it the most Protestant of the Six Counties. In fact settlement across the narrow seas separating Antrim from Galloway and Kintyre was not uncommon: one of the most significant movements in the history of the British Isles had occurred in the other direction a millennium before, when people whom the Romans had called Scots crossed from the Kingdom of Dalriada in northern Antrim to found a new Dalriada in Argyll.
The county was formed in 1570, perhaps in 1560, and took its name from the town on the northeastern shores of Lough Neagh. Belfast was negligible then, but by the time elected county government came in, by the Act of 1898, Belfast was Ireland’s major industrial city and it was given county borough status.
In 1974 the county lost its administrative functions to new district councils: Moyle, Ballymoney, Ballymena, Larne, Carrickfergus, Newtownabbey, and Antrim, all within the county; and Lisburn, from Cos Antrim and Down (Belfast too stood on land from both counties). Co. Antrim survives for ceremonial purposes, with its Lord Lieutenant (within the city of Belfast, the Lord Mayor undertakes the duties of the Lord Lieutenant).
Connor, within the county, was the medieval diocese but it united with its southern neighbour to form Down & Connor in 1441. A separate diocese was re-created in the Church of Ireland in 1945.