1971 Indianapolis 500

The 55th 500 Mile International Sweepstakes was a motor race 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.

The race was marred by a crash involving the pace car at the start. Eldon Palmer, a local Indianapolis-area Dodge dealer, lost control of the Dodge Challenger pace car at the south end of the pit area, and it crashed into a photographers' stand, injuring 29 people, two seriously.

Peter Revson started on the pole with a record speed of 178.696 miles per hour (287.6 km/h), more than a mile per hour faster than any other qualifier, with defending Indy 500 winner and USAC National Champion Al Unser in the middle of the second row. Mark Donohue, who qualified in the middle of the front row, took the lead at the start of the race and led the first 50 laps. A mechanical issue ended his day, however, on lap 66, at which time Unser assumed the lead. He and Joe Leonard swapped the lead several times during the middle portion of the race, but Unser led for the final 83 laps, giving him a win for the second year in a row. He was the first to successfully defend his title since Bill Vukovich won in 1953–1954.

Unser became the first and only driver to-date to win the race on his birthday (32nd); which was also coincidentally the first time the race had ever been held on May 29, and he also became the first winner to celebrate in the new victory lane. The new winner's area, now featuring black and white checkered ramps, was moved from the south end of the pits to the "horseshoe" area immediately below the Master Control Tower, near the start/finish line.

The 1971 Indy 500 was part of the newly re-organized USAC Marlboro Championship Trail, in which dirt tracks were separated from the paved ovals and road courses. From then on, the Gold Crown championship schedule would consist solely of paved tracks (both ovals and road courses), giving the national championship a decidedly new look for the 1970s and beyond. In addition, with 500-mile races at Ontario and Pocono now on the schedule, Indy car racing formed its first "triple crown."

The city of Indianapolis celebrated its Sesquicentennial in 1971, and the occasion was reflected on the bronze and silver pit badges for the month of May. During the week leading up to the race, Indianapolis was also the site of 1971 NATO International Conference of Cities.