Viscount Castlereagh (1769-1822)
Robert Stewart, 2nd Marquess of Londonderry, KG, GCH, PC (18 June 1769 - 12 August 1822), known until 1821 by his courtesy title of Viscount Castlereagh, was an Anglo-Irish politician born in Dublin who represented the United Kingdom at the Congress of Vienna.
He was also intimately involved in securing the passage of the controversial Irish Act of Union. He was the son of Robert Stewart, 1st Marquess of Londonderry, a landowner who was created an earl and subsequently a marquess by King George III of the United Kingdom. He received his early education at The Royal School, Armagh, and later attended St. John's College, Cambridge for a single year. Additionally, the elder Robert Stewart was also known as The Viscount Castlereagh for about one year.
Robert Stewart acquired the courtesy title Viscount Castlereagh in 1796 when his father was created Earl of Londonderry, and is generally known to history by that title. He became briefly 2nd Marquess of Londonderry in the Peerage of Ireland on the death of his father in 1821.