Jason C. Leffler (September 16, 1975 – June 12, 2013) was an American professional open-wheel and driver. Leffler began racing in the open-wheel ranks, competing in the 2000 Indianapolis 500 before moving to primarily NASCAR competition. He died from injuries sustained in a 410 sprint car race at Bridgeport Speedway in Bridgeport, New Jersey.

Leffler began his career racing midget cars in the USAC series, where he won three consecutive midget championships from 1997 and 1999, as well as the Silver Crown series championship in 1998. He was the third driver to win three consecutive midget car championships. He won the Hut Hundred and Belleville Nationals in 1997, and the Turkey Night Grand Prix and Copper Classic in 1999. He won his second Turkey Night Grand Prix in 2005.

Roger Penske met Leffler at the 1998 Hut 100. Leffler's success also caught the attention of Joe Gibbs Racing, a team which had previously signed Tony Stewart from the USAC ranks. Leffler joined the team in 1999 and made four starts in the Busch Series during the season with moderate success. At the same time, he also started a race in the Indy Racing League at Walt Disney World Speedway in the No. 5 Treadway Racing machine, but finished last after crashing early in the race.

Leffler made his first, and only, start in the Indianapolis 500 in 2000. This effort was put forth by Treadway Racing with backing from Roger Penske's United Auto group. Leffler qualified in the 17th position, which was also where he finished.

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