The 1948 United States presidential election was the 41st quadrennial presidential election. It was held on Tuesday, November 2, 1948. In one of the greatest election upsets in American history, incumbent Democratic President Harry S. Truman defeated heavily favored Republican New York Governor Thomas E. Dewey, and third-party candidates, becoming the third president to succeed to the presidency upon his predecessor's death and be elected to a full term.

Harry S. Truman was the 33rd president of the United States, serving from 1945 to 1953. A member of the Democratic Party, he previously served as a United States senator from Missouri from 1935 to 1945 and briefly as the 34th vice president in 1945 under Franklin D. Roosevelt. Assuming the presidency after Roosevelt's death, Truman implemented the Marshall Plan in the wake of World War II to rebuild the economy of Western Europe and established both the Truman Doctrine and NATO to contain the expansion of Soviet communism. He proposed numerous liberal domestic reforms, but few were enacted by the conservative coalition that dominated the Congress.