Baron Rathcavan, of The Braid in the County of Antrim, is a title in the Peerage of the United Kingdom. It was created in 1953 for the Unionist politician Sir Hugh O'Neill, 1st Baronet. He had already been created a Baronet, of Cleggan in the County of Antrim, in 1929. O'Neill was the third son of Edward O'Neill, 2nd Baron O'Neill (see the Baron O'Neill for earlier history of the family) and the uncle of the Prime Minister of Northern Ireland Terence O'Neill, Baron O'Neill of the Maine. Lord Rathcavan was also a male-line descendant of Edward Chichester, 1st Viscount Chichester (see the Marquess of Donegall). He was succeeded by his eldest surviving son, the second Baron. He succeeded his father as Unionist Member of Parliament for Antrim in 1952, a seat he held until 1959, and was later a member of the Parliament of Northern Ireland. As of 2014[update] the titles are held by his son, the third Baron, who succeeded in 1994. As a descendant of both the second Baron O'Neill and the first Viscount Chichester, Lord Rathcavan is in remainder to the barony of O'Neill as well as to the viscountcy of Chichester and the earldom of Donegall.
The Honourable Sir Con O'Neill, second son of the first Baron, was a diplomat. His daughter Baroness O'Neill of Bengarve is a philosopher.