Iveagh (/ˈaɪveɪ/ EYE-vay; from Irish Uíbh Eachach, meaning 'descendants of Echu'[1]) is the name of several historical territorial divisions in what is now County Down, Northern Ireland.

Originally it was a Gaelic Irish territory, ruled by the Uí Echach Cobo and part of the overkingdom of Ulaid.

[8] The ancestor of the Uí Echach Cobo, Eochaid mac Condlai, descends from Fiachu Araide, eponymous founder of Dál nAraidi.

The first to be mentioned in the annals is Aodh Ua hAitidhe, king of Uí Echach Cobo, who was killed by his own people in AD965.

[8] The last mention is under AD1136 where Echri Ua hAitidhe, lord of Uí Echach Cobo was killed, likewise by his own people.

[13] One early mention is in 1153 with the granting of the charter to the abbey of Newry which was witnessed by Aedh Mor Magennis, chief of Clann Aodha, of Iveagh.

[8] The Mac Aonghusa are also mentioned in letters by King Edward II, where they are titled Dux Hibernicorum de Ouehagh, meaning "chief of the Irish of Iveagh".

[15] In 1539 a cattle raid into County Meath was intercepted by Lord Deputy Grey and the clan was defeated at the Battle of Bellahoe.

In 1543 the then chief Art MacArtáin of Rathfriland accepted the new policy of "Surrender and regrant" and travelled to Greenwich Palace to be knighted as Sir Arthur Guinez by King Henry VIII.

Despite this, Charles Blount, the Lord Deputy of Ireland, ravaged Iveagh to the point that its chief Art Roe Magennis submitted to prevent the extermination of his people.