Viscount Castlereagh, born Robert Stewart in 1769, was a prominent British statesman known for his role in the early 19th century. He served as the Secretary of State for Foreign Affairs and played a key part in the Congress of Vienna, which aimed to restore stability in Europe after the Napoleonic Wars. His diplomatic efforts helped shape the balance of power in Europe. Castlereagh was a member of the Tory Party and held various political positions throughout his career. He was instrumental in forming alliances and treaties, including the Quadruple Alliance, which united Britain, Austria, Prussia, and Russia against France. His legacy is marked by his contributions to European diplomacy and peacekeeping.