The 1900 United States presidential election in Illinois took place on November 6, 1900. All contemporary 45 states were part of the 1900 United States presidential election. State voters chose 24 electors to the Electoral College, which selected the president and vice president.

The 1900 United States presidential election was the 29th quadrennial presidential election, held on Tuesday, November 6, 1900. In a re-match of the 1896 race, incumbent Republican President William McKinley defeated his Democratic challenger, William Jennings Bryan. McKinley's victory made him the first president to win a consecutive re-election since Ulysses S. Grant accomplished the same feat in 1872. Until 1956, this would be the last time in which an incumbent Republican president would win re-election after serving a full term in office. This election saw the fifth rematch in presidential history, something that would also not occur again until 1956. This was also the first rematch to produce the same winner both times.