Hornish passes Andretti as they come up to the finish line in the Indy 500

The American overcame a pit-lane error and losing a lap late in the race to pass the 19-year-old on the run to the line and win by a single car length.

Andretti finished one second ahead of his 43-year-old father Michael, who was returning after a two-year absence.

The 2005 winner Dan Wheldon was fourth, after leading at one stage, with fellow Briton Dario Franchitti seventh.

Hornish was penalised for leaving his pit with the fuel hose still connected to his Dallara-Honda, but he stayed in touch with the leaders.

Michael Andretti led with five laps to go before being overtaken by son Marco and Hornish also passed the veteran to chase down Andretti Jr.

It's a great feeling. I wouldn't trade it for anything else Sam Hornish

Hornish closed too rapidly with two laps to go and nearly ran into Marco's back in the third turn.

But, somehow, Hornish was able to recover and his final lap was nearly 5.5 miles per hour faster than Marco's.

Coming down to the finish line, he drove to the inside of his rival and crossed it six hundredths of a second in front.

Hornish, whose previous best finish in the race was 14th in 2001, is the 65th different winner of the race in its 90-year history.

He was also a record 14th winner for team owner Roger Penske.

"Not everything went our way but we stuck together as a team, we had a plan and we had the speed when we needed it," he said.

"It's a great feeling. I wouldn't trade it for anything else."

Englishman Wheldon was bitterly disappointed not to have retained the title after leading for 148 of the 200 laps.

"It's disappointing we got a puncture and had to pit off-sequence. It's just tough," said the 27-year-old.

"I had a very good car. It's very good in traffic. It was good all day long, but we didn't win."