Robert Stewart, Viscount Castlereagh
British politician (1769–1822)
Robert Stewart, 2nd Marquess of Londonderry (18 June 1769 – 12 August 1822), usually known as Lord Castlereagh, derived from the courtesy title Viscount Castlereagh (UK: KAH-səl-ray) by which he was styled from 1796 to 1821, was a British statesman. As secretary to the Viceroy in Ireland, he worked to suppress the Rebellion of 1798 and to secure passage in 1800 of the Irish Act of Union. As the Foreign Secretary of the United Kingdom from 1812, he was central to the management of the coalition that defeated Napoleon, and was British plenipotentiary at the Congress of Vienna. In the post-war government of Lord Liverpool, Castlereagh was seen to support harsh measures against agitation for reform, and he ended his life an isolated and unpopular figure.
Early in his career in Ireland, and following a visit to revolutionary France, Castlereagh recoiled from the democratic politics of his Presbyterian constituents in Ulster. Crossing the floor of the Irish House of Commons in support of the government, he took a leading role in detaining members of the republican conspiracy, the United Irishmen, his former political associates among them. After the 1798 Rebellion, as Chief Secretary for Ireland he pushed the Act of Union through the Irish Parliament. However, unable to overcome the resistance of King George III to the Catholic Emancipation that they believed should have accompanied the creation of a United Kingdom, both he and Prime Minister William Pitt resigned.
From 1805 Castlereagh served as Secretary of State for War in Pitt's second administration and, from 1806, under the Duke of Portland. In 1809 he was obliged to resign after fighting a duel with the foreign secretary, George Canning.
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Biographical claims are most persuasive when dates, appointments and relationships can be traced to records created close to the events described. The source revision retrieved here is dated Sep 11, 2026. The linked authority identifier is Q333050. VIAF identifies the subject as 15560591. The Library of Congress control number is n50041547. 3 of 3 selected statements include explicit references; 0 carry qualifiers and 0 use preferred rank. The first chronological checks are 1769, 1822, 1796 and 1821.
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This entry incorporates text from “Robert Stewart, Viscount Castlereagh” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.