O'Neill, Conn (d. 1619), lord of Upper Clandeboye (Clann Aodha Bhuidhe Uachtar), was one of the five sons of Niall O'Neill, lord of Upper Clandeboye. Through the political agility of Conn's father in switching from the side of Hugh O'Neill (qv), 2nd earl of Tyrone, to that of the government, many of the remaining lands of the eastern O'Neill lordship of Clandeboye were preserved. When Niall died in Carrickfergus (February 1601) both he and Conn were in the pay of the English army. Conn's claim to succeed his father as lord was disputed by his cousin Eóghan. The government at first divided the territory between the claimants, but then settled it solely on Conn. On hearing the news of the Spanish landing at Kinsale (September 1601), Conn joined the cause of Hugh O'Neill. His rebellion was brief and he was imprisoned in Carrickfergus. Through the intercession of English commanders, he was pardoned and allowed to return to his castle of Castlereagh.
It was not long before Conn was again imprisoned. It seems that he gave a feast within days of the death of Elizabeth, and during the proceedings was shocked to learn that his store of wine was diminishing rapidly. He then despatched his men to Carrickfergus to buy some wine. While there they were set on by soldiers, who beat them and relieved them of their purchases, forcing them to return empty-handed to Conn. On hearing the tale, Conn ordered them back to Carrickfergus to retake the wine while he and his friends took up a position on a hill to watch the spectacle. Conn's men were easily beaten by the garrison, but unfortunately for him this incident was transformed into a rebellion and he was again imprisoned.
During his confinement he was allowed to frequent the taverns of Carrickfergus, where he was approached by envoys of Hugh Montgomery, laird of Braidstone in Scotland. They offered to help him escape and promised that their master would intercede with James I for Conn's pardon; in turn, Conn was to sign over a half of his lands to Montgomery. Conn agreed, and he was farcically kidnapped by the Scots from Carrickfergus. Once in Scotland he made his way to Montgomery and signed the agreement, and together they made their way to the English court to secure his pardon. When this was achieved their agreement was ratified and passed under the great seal. Unfortunately for Conn another Scot, James Hamilton (qv), later Viscount Clandeboye, persuaded the king that the grant was too big for the two men, and that he should have a share. The grant was then redivided between Hamilton, Montgomery, and Conn. This did not mark the end of Conn's problems, and during the next decade he sold, leased, and mortgaged most of his remaining lands, even Castlereagh (1616). He died in 1619, leaving an estate worth £12,000 a year to his eldest son and heir, Daniel O'Neill (qv).
He married the daughter of Art O'Neill, brother to Hugh O'Neill; they had three recorded sons and one daughter. His lordship of Clandeboye was characterised by his lack of judgement and dissolute ways, which squandered the advantages his father's judicious policies had snatched from the Elizabethan conquest.