An Irish Catholic noble and military leader, he was born January 1658, the son of Sir Henry O'Neill, 1st Baronet of Killeleagh and Eleanor, daughter of Sir William Talbot, 1st Baronet. His genealogy is Neil son of Henry son of Niall Oge son of Niall son of Hugh son of Felim Baccach son of Niall Mor son of Conn son of Aodh Buidhe son of Brian Ballach son of Muircheartach Cennfhada, Chief of Clandeboy son of Henry, King of Tír Eóghain County Tyrone. O'Neill was appointed Lord Lieutenant of Armagh by King James II of England in 1689. He led 800 Jacobite dragoons at the Battle of the Boyne against English troops under The 3rd Duke of Schomberg and fell in this attack. He was wounded in the battle, near Slane. He was carried first to Dublin and thence to Waterford where he died of his wounds due to the negligence of his surgeons. His grave is in the cemetery of the French Church in Waterford; the gravestone reads:
"Here lyes the body of S. Neal O'Neill, Baronet of Killelag in the County of Antrim, who dyed ye 8th of July, in the year 1690, at the age of 32 years and six months. He married the second daughter of Lord Viscount Molyneux, of Sefton, in Lancashire, in England. Reguiescant in Pace."
Family
O'Neill married in 1677 or 1683 Frances Molyneux, second daughter of The 3rd Viscount Molyneux, the Lord Lieutenant of Lancashire, and his wife Mary Barlow. With her he had at least four daughters: Rose, Mary, Elizabeth and Ann. His wife and daughters were painted by the Irish painter Garret Murphy c.1700. Rose married Nicholas Wogan of Rathcoffey, and Anne married John Segrave. As he had no son, the title passed to his brother Daniel, but was forfeited in 1691. Daniel managed to retain much of the family estates, but as his brother had died deeply in debt, he was obliged to sell Killyleagh in 1703. Frances died in 1732. His only sister Rose, foster daughter of Rose O'Neill the Marchioness of Antrim, married Captain Con Modera O'Neill, son of Colonel Con mac Brian O'Neill, both of whom fought with him at the Battle of Boyne, and the former leading the heroic efforts of the Irish forces at the Second Siege of Aughrim.
