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.

Robert Stewart, Viscount Castlereagh (born June 18, 1769, Dublin—died Aug. 12, 1822, London) was a British foreign secretary (1812–22), who helped guide the Grand Alliance against Napoleon and was a major participant in the Congress of Vienna, which redrew the map of Europe in 1815.

Castlereagh (/ ˈ k ɑː s əl r eɪ / KAH-səl-ray) was a local government district with the status of borough in Northern Ireland. It merged with Lisburn City Council in May 2015 under local government reorganisation in Northern Ireland to become Lisburn and Castlereagh City Council, with a small amount being transferred to Belfast City Council.

Robert Stewart, Viscount Castlereagh (1769–1822), later 2nd Marquess of Londonderry: Anglo-Irish statesman and British Foreign Secretary.

Robert Stewart, Viscount Castlereagh and 2nd Marquis of Londonderry, politician, was buried in the centre of the north transept of Westminster Abbey, to the south of the grave of William Pitt and his son. The inscription on his grave has now worn away but it read:

As chief secretary for Ireland (1798–1801), Castlereagh singlehandedly forced the Act of Union through the Irish Parliament in 1800. He served as Britain’s secretary for war (1805–06, 1807–09) and as secretary for foreign affairs and leader of the House of Commons (1812–22).

Robert Stewart, Viscount Castlereagh and Second Marquess of Londonderry's tenure as one of Britain's most influential foreign secretaries (1812–1822) coincided with a period of considerable tumult both at home and abroad.

2018年6月27日 · Castlereagh, Robert Stewart, 2nd Viscount (1769–1822) British politician. Castlereagh was chief secretary of Ireland (1799–1801), and helped secure the passage of the Act of Union with Britain in 1800.

The British statesman Robert Stewart Viscount Castlereagh and 2d Marquess of Londonderry (1769-1822), as foreign secretary did much to consolidate a firm final international alliance against Napoleon and to establish the framework for a remarkably durable European peace settlement.

Castlereagh, former district (1973–2015) located directly southeast of Belfast, astride the former counties of Down and Antrim, now part of the Lisburn and Castlereagh City district, Northern Ireland.