The 55th 500 Mile International Sweepstakes was held at the Indianapolis Motor Speedway in Speedway, Indiana on Saturday, May 29, 1971. Al Unser Sr. won for the second consecutive year, dominating most of the race. Unser became the fourth driver to win the Indy 500 in back-to-back years, and it was his second of a record-tying four Indy victories.