This thesis is a study of the diplomacy of George Canning between September 1822 and July 1824. It offers a detailed analysis of Canning's diplomacy on all the major international questions of the period in which his country's vital interests were involved. Those questions were: (1) the Franco-Spanish crisis in 1822-3 and the French intervention in Spain in 1823; (2) the affairs of Spanish America including the question of the independence of Spain's former colonies and that of the future of Cuba; (3) political instability in European Portugal; (4) the question of Brazilian independence; (5) the Greek War of Independence and the Russo-Turkish crisis. This study challenges and revises the existing accounts of Canning's diplomacy on these questions in many important points. However, it is not merely a narrative account of Canning's diplomacy, but also an attempt to present a clear and comprehensive picture of the system of his diplomacy and some general principles which guided it. It pays particular attention to the relations between Canning's diplomacy and the Concert of Europe-the post-1815 system of great-power co-operation in Europe. It has been generally believed that Canning was an isolationist whose principal aim in foreign policy was to destroy this system of great-power co-operation - which he believed was ideologically unacceptable to Britain and was unduly restraining her freedom of action-and replace it with a more fluid eighteenth-century-style balance-of-power system - which he believed would give Britain greater freedom of action and would be more beneficial to her interests and influence in and outside Europe. This study challenges this widely accepted view, and argues that Canning's aim was not to break up the system of great-power concert entirely but to transform it into such a shape that would be acceptable both to Britain and to the powers of the continent.