Location of the former barony of Iveagh, County Down, in present-day Northern Ireland. It was based on the Irish district of Uíbh Eachach, which was ruled for several centuries by the Magennis clan
Magennis, also spelled Maguiness, Maginnis, McGuinness or Guinness, is an Irish surname, derived from the Gaelic Mac Aonghusa, meaning the "descendants of Angus", which in eastern Ulster was commonly pronounced as Mag Aonghusa. A prominent branch of the Uíbh Eachach Cobha, the Magennises would become chiefs of the territory of Iveagh, which by the 16th century comprised over half of modern County Down, Northern Ireland. By the end of the 17th century, their territory had been divided up between them and British prospectors.
The four main branches of the Magennis clan were: Castlewellan, Corgary, Kilwarlin, and Rathfriland, of which there was rivalry between. The Mac Artáin (MacCartan) sept of Kinelarty, descend from the Magennis clan, through the great-grandson of Mongán Mac Aonghusa.
The Magennis clan were a sept of the Ui hAitidhe, and descended from Sárán, a descendant of Eachach Cobha, of which the territory of Uíbh Eachach Cobha (Iveagh) derived its name. They ruled the sub-territory of Clann Aodha (Clan Hugh), however by the 12th-century had replaced the Ui hAitidhe as the chiefs of Iveagh, with Rathfriland as their base.
One of the earliest mentions of the Magennis as chiefs of Iveagh, is in the charter granted to the abbey of Newry in 1153, which was witnessed by Aedh Mor Magennis, who was cited as being chief of Clann Aodha and of Iveagh. The Magennises are also mentioned in letters by King Edward II, where they are titled Dux Hibernicorum de Ouehagh, meaning "chief of the Irish of Iveagh".
The Magennises allied themselves to the Earldom of Ulster, which was created after the Norman invasion of Ulster, until the death of William Donn de Burgh, 3rd Earl of Ulster in 1333. After the subsequent collapse of the earldom, the Magennises by the 15th century had expanded Iveagh all the way east to Dundrum Castle, where County Down meets the Irish Sea.
By 1500 there were twelve branches of the Magennis clan, the most prominent being: Castlewellan, Corgary, Kilwarlin, and Rathfriland, of which rivalry between threatened the cohesion of Iveagh. Throughout the 16th century, the Magennis clan ensured they remained on good terms with the English. One chief, "Arthur Guinez", was on the losing side in the Battle of Bellahoe in 1539. Art MacPhelim Magennis of Castlewellan (possibly the same man as Arthur Guinez) and Donal Óg Magennis of Rathfriland were both given knighthoods in 1542.
Sir Hugh Magennis, the son of Donal Óg Magennis, was called by Sir Henry Bagenal the "civillist of all the Irishry", with Sir Nicholas Bagnall cited as having brought Sir Hugh over to the Queen's side from that of O'Neills. In 1584 Sir Hugh was regranted 'the entire country or territory of Iveagh', but not including the territory of Kilwarlin. When Sir Hugh died in 1596, his heir was his son Art Roe Magennis, whose sister Catherine was married to Hugh O'Neill. As such Art Roe joined Hugh's side in the Nine Years' War against the English. During this war, Lord Mountjoy, the Lord Deputy of Ireland, ravaged Iveagh to the point where Art Roe Magennis submitted to prevent the extermination of his people, and as such was promised he could keep his lands.
Following the Nine Years' War and just before the process of colonising Ulster with loyal Protestant subjects, the arrangement of dividing mighty Gaelic lordships into smaller weaker lordships, such as what happened in County Monaghan with the MacMahon's, occurred with Iveagh. In 1605 the "Commission for the Division and Bounding of the Lords" was established to replicate the Monaghan arrangement, with Art Roe Magennis applying to be made Lord Iveagh. In February 1607, the commission however decided to break up Iveagh, a process that continued until 1610, seeing the creation of fifteen freeholds. The Magennises where granted thirteen of these freeholds, with Art Roe being granted the largest. The rest however was given to officers in the Crown forces, most of whom had served in the Nine Years' War under Sir Henry Bagenal and Sir Arthur Chichester. 
Amongst the freehold grants to the Magennises where:
- Ever MacPhelimy Magennis of Castlewellan, who was granted eleven townlands, constituting the Castlewellan estate in the parishes of Kilmegan and Drumgooland.
- Brian MacHugh MacAgholy Magennis of Muntereddy, who was granted seven and a half townlands, constituting the Bryansford estate in the parishes of Maghera (Bryansford) and Kilcoo. This estate was held by the Earl of Roden on account of his descent from Brian.
Sir Arthur Magennus, stated as being chief of the Magennises in 1610, granted from his own large estate to his kin:
- Glassney Roe Magennis of Ballymoney, three townlands.
- Fer-doragh MacFellimey MacPrior Magennis of Clanvarraghan, three townlands in Kilmegan parish.
The lands the Magennises held in these Iveagh freeholds diminished as the officers and other speculators went about extending their possessions at their expense through legal and illegal means. The failure of the native Irish to properly understand the English legal system resulted in them accruing large debts resulting in them having to sell vast swathes of their lands or losing them as collateral when they failed to pay their debts. Despite finally being appointed Lord Iveagh in 1623, Art Roe Magennis also found himself in a dangerous financial position.
The Scottish landowners Sir James Hamilton and Sir Hugh Montgomery, looked to County Down to expand their own holdings in Ulster, and acquired lands in Iveagh, Kinelarty and Lecale, dislocating the local Irish such as the Magennises and MacCartans.
Many of the disgruntled and dispossessed Magennises joined in the Irish rebellion of 1641 and the subsequent War of the Three Kingdoms, with two of the six Ulster delegates on the Confederate Supreme Council being Magennises. Following this and the Cromwellian conquest of Ireland, the Magennises of Iveagh lost out significantly with all their lands but those at Tollymore being forfeited, with four of the leading Magennis freeholders transplanted to the province of Connacht. Following the Restoration of the British monarchy in 1660, King Charles II restored Phelimy Magennis and his son Ever to their Castlewellan estates upon their conversion to Protestantism. The king also sought to have the 3rd Viscount Iveagh, Arthur Magennis, restored, however this was prevented by local landowners.
The viscountcy lasted from 1623 to 1693 in the peerage of Ireland:
- Art Roe (d 1629); created viscount in 1623; married to Sarah, a daughter of Hugh O'Neill, Earl of Tyrone
- Hugh (1599-1639); married Mary Bellew of Bellewstown
- Arthur (d. 1683); married Margaret O'Reilly.
- Hugh (1630–84); married Rose O'Neill
- Bryan (d.1692); married Lady Margaret de Burgh or Burke, daughter of William Burke, 7th Earl of Clanricarde
- Phelim (d. before 1701)
- See also, List of people named McGuinness.
- James Joseph Magennis (1919-1986), Northern Irish recipient of the Victoria Cross
- Josh Magennis (born 1990), Northern Irish professional footballer
- William Magennis (1867-1946), Irish politician and university professor
The name can also be spelt "McGuinness", as in:
- John McGuinness (disambiguation)
- Paddy McGuinness, comedian from Greater Manchester
- Paul McGuinness, manager of U2
- Martin McGuinness
- Mairead McGuinness
In America the name is more often spelt "Maginnis"; see:
- The Baron Maginnis of Drumglass (born 1938), Northern Irish politician
- John Maginnis
- Charles Donagh Maginnis
- John Maginnis
- Martin Maginnis
- Niall MacGinnis
- Robert L. Maginnis
- Robert P. Maginnis
- Ross A. McGinnis
- Maginnis & Walsh
Other variant spellings include:
The heir of the former lords of Iveagh was created Viscount Magennis of Iveagh in the Irish peerage in 1623 by King James I of England. The title was attainted in 1693 after the Williamite war. Claiming a descent from the Magennis clan, Sir Edward Guinness took the title Lord Iveagh in 1891, and then Earl of Iveagh in 1919. In 2001 Ken Maginnis was granted a life peerage as Baron Maginnis of Drumglass.
- Dundrum Castle, Norman castle in County Down, formerly known as Magennis castle.
The Border Chieftains of Ulster
||O'Hanlon Sept||McCann Sept||Belfast|
|O'Hanlon Sept||English Ulster|
|O'Hanlon Sept||Newry||Mourne Mountains|
- Cite error: The named reference was invoked but never defined.
- Robert Bell (2003). The book of Ulster Surnames. The Blackstaff Press. pp. 163–4. ISBN 0-85640-602-3.
- Library Ireland - The barony of Iveagh
- Jonathan Bardon (2011). The Plantation of Ulster. Gill & Macmillan. ISBN 978-0-7171-4738-0.
- Proudfoot L. (ed.) Down History and Society (Dublin 1997) ISBN 0-906602-80-7 PP162-3
- G. E. Cokayne, The Complete Peerage, Vol. VIII (London: The St. Catherine Press, 1932), p. 350, note (b)
- Proudfoot L. (ed.) Down History and Society (Dublin 1997) ISBN 0-906602-80-7