Robert William Hugh O'Neill, 1st Baron Rathcavan PC
) was an Ulster Unionist
member of both the UK Parliament
and the Parliament of Northern Ireland
He served as a Major in the British Army. First elected to the Westminster Parliament in for Mid Antrim in 1915, he later represented Antrim and then North Antrim in Northern Ireland.
O'Neill was also elected to represent Antrim in the Northern Ireland House of Commons in 1921 and served as its first Speaker, before standing down from his seat in 1929.
From 1933-39, he was the Chairman of the 1922 Committee. He also sat on the Privy Council of Ireland, its successor, the Privy Council of Northern Ireland and the Privy Council of the United Kingdom. From 1939 to 1940, he was the Parliamentary Under-Secretary of State for India and Burma, and was the Lord Lieutenant of Antrim from 1949 to 1959.
O'Neill retired from the Westminster Parliament in 1952, having become the Father of the House the previous year, and was created 1st Lord Rathcavan in 1953.