The foreign relations of Canada are Canada's relations with other governments and peoples. Canada's most important relationship, being the largest trading relationship in the world, is with the United States. However, Canadian governments have traditionally maintained active relations with other nations, mostly through multilateral organizations such as the United Nations, the Commonwealth of Nations, La Francophonie, the Organization of American States, and the North Atlantic Treaty Organization (NATO).
The British North American colonies which today constitute modern Canada had little control over their foreign affairs until the achievement of responsible government in the late 1840s. Up to that time, wars, negotiations and treaties were carried out by the British government to settle disputes concerning the colonies over fishing and boundaries and to promote trade. Notable examples from the colonial period include the Nootka Convention, the War of 1812, the Rush–Bagot Treaty, the Treaty of 1818, the Webster–Ashburton Treaty, and the Oregon Treaty. Before the granting of responsible government, British diplomats handled foreign affairs and had the goal of achieving British goals, especially peace with the United States; domestic Canadian interests were secondary. The Canadian–American Reciprocity Treaty of 1854 signaled an important change in relations between Britain and its North American colonies. In this treaty, the Canadas were allowed to impose tariff duties more favourable to a foreign country (the U.S.) than to Britain, a precedent that was extended by new tariffs in 1859, 1879 and 1887, despite angry demands on the part of British industrialists that these tariffs be disallowed by London.