Franklin Delano Roosevelt (January 30, 1882 – April 12, 1945), commonly known by his initials FDR, was an American politician who served as the 32nd president of the United States from 1933 until his death in 1945. The longest serving U.S. president, he is the only president to have served more than two terms. His initial two terms were centered on combating the Great Depression, while his third and fourth saw him shift his focus to America's involvement in World War II.

A member of the prominent Delano and Roosevelt families, Roosevelt was elected to the New York State Senate from 1911 to 1913 and was then the assistant secretary of the Navy under President Woodrow Wilson during World War I. Roosevelt was James M. Cox's running mate on the Democratic Party's ticket in the 1920 U.S. presidential election, but Cox lost to Republican nominee Warren G. Harding. In 1921, Roosevelt contracted a paralytic illness that permanently paralyzed his legs. Partly through the encouragement of his wife, Eleanor Roosevelt, he returned to public office as governor of New York from 1929 to 1933, during which he promoted programs to combat the Great Depression. In the 1932 presidential election, Roosevelt defeated president Herbert Hoover in a landslide victory.

During his first 100 days as president, Roosevelt spearheaded unprecedented federal legislation and directed the federal government during most of the Great Depression, implementing the New Deal, building the New Deal coalition, and realigning American politics into the Fifth Party System. He created numerous programs to provide relief to the unemployed and farmers while seeking economic recovery with the National Recovery Administration and other programs. He also instituted major regulatory reforms related to finance, communications, and labor, and presided over the end of Prohibition. In 1936, Roosevelt won a landslide reelection.