Harry S. Truman (May 8, 1884 – December 26, 1972) was the 33rd president of the United States from 1945 to 1953, succeeding upon the death of Franklin D. Roosevelt after serving as vice president. He implemented the Marshall Plan to rebuild the economy of Western Europe, and established the Truman Doctrine and NATO.

Truman was elected to the United States Senate in 1934 and gained national prominence as chairman of the Truman Committee aimed at reducing waste and inefficiency in wartime contracts. Soon after succeeding to the presidency he authorized the first and only use of nuclear weapons in war. Truman's administration engaged in an internationalist foreign policy and renounced isolationism. He rallied his New Deal coalition during the 1948 presidential election and won a surprise victory that secured his own presidential term.

Truman oversaw the Berlin Airlift of 1948. When North Korea invaded South Korea in 1950, he gained United Nations approval for the very large policy action known as the Korean War. It saved South Korea but the Chinese intervened, driving back the UN/US forces and preventing a rollback of communism in North Korea. On domestic issues, bills endorsed by Truman faced opposition from a conservative Congress, but his administration successfully guided the U.S. economy through the post-war economic challenges. In 1948 he submitted the first comprehensive civil rights legislation and issued Executive Orders to start racial integration in the military and federal agencies.

Corruption in the Truman administration became a central campaign issue in the 1952 presidential election. After Republican Dwight D. Eisenhower's electoral victory against Democrat Adlai Stevenson II, Truman went into a financially-difficult retirement, marked by the founding of his presidential library and the publication of his memoirs. When he left office, Truman's presidency was criticized, but scholars rehabilitated his image in the 1960s and he is highly ranked by scholars.