The Truman Doctrine is an American foreign policy that pledges American "support for democracies against authoritarian threats." The doctrine originated with the primary goal of countering the growth of the Soviet bloc during the Cold War. It was announced to Congress by President Harry S. Truman on March 12, 1947, and further developed on July 4, 1948, when he pledged to oppose the communist rebellions in Greece and Soviet demands from Turkey. More generally, the Truman Doctrine implied American support for other nations threatened by Moscow. It led to the formation of NATO in 1949. Historians often use Truman's speech to Congress on March 12, 1947 to date the start of the Cold War.

The officially stated goals of the foreign policy of the United States of America, including all the bureaus and offices in the United States Department of State, as mentioned in the Foreign Policy Agenda of the Department of State, are "to build and sustain a more democratic, secure, and prosperous world for the benefit of the American people and the international community". Liberalism has been a key component of US foreign policy since its independence from Britain. Since the end of World War II, the United States has had a grand strategy which has been characterized as being oriented around primacy, "deep engagement", and/or liberal hegemony. This strategy entails that the United States maintains military predominance; builds and maintains an extensive network of allies ; integrates other states into US-designed international institutions ; and limits the spread of nuclear weapons.