Hayden won the first American MotoGP for 11 years

Hayden started from pole on the Honda and led throughout the 32-lap race, finishing ahead of Yamaha riders Colin Edwards and Valentino Rossi.

Rossi's run of five straight wins ended but the Italian extended his world championship lead after rival Marco Melandri crashed on the first lap.

Britain's Shane Byrne came in 15th on his Proton KR.

Hayden's previous best finish was third in Germany last year.

"My team and my bike, just everything felt good today and it just clicked," said the 23-year-old.

"I just got out front and just kept going as hard as I could. Sometimes I would see the gap get small and I just rode my heart out and kept pushing.

"Today was my day thanks to my team. I mean these guys pushed me hard... every dog has his day."

We had some problems. We are not at 100% Valentino Rossi

Rossi was highly critical of the Laguna Seca circuit in the lead-up to the race and at the end, had to settle for his worst finish of the season.

The Italian was passed by team-mate Edwards with a deft inside move into the Corkscrew turn on the 16th of 28 laps.

Rossi attacked at the end of the race, closing to 0.371 seconds of Edwards, but had to settle for third on the podium.

"I'm happy because we have always been on the podium this year," said Rossi.

"But we had some problems. We are not at 100%."

Italian Max Biaggi was fourth and remains third in the standings, although he closed to within seven points of Melandri.

Melandri, who also crashed in practice and qualifying, did not complete a lap after colliding with Brazilian Alex Barros.

The US Grand Prix is the only event on the calendar that does not include the 125cc and 250cc classes.

Results from US MotoGP, Laguna Seca:
1. Nicky Hayden (United States) Honda 45:15.374
2. Colin Edwards (United States) Yamaha 45:17.315
3. Valentino Rossi (Italy) Yamaha 45:17.686
4. Max Biaggi (Italy) Honda 45:19.590
5. Sete Gibernau (Spain) Honda 45:19.852
6. Troy Bayliss (Australia) Honda 45:37.755
7. Makoto Tamada (Japan) Honda 45:37.867
8. John Hopkins (United States) Suzuki 45:38.522
9. Shinya Nakano (Japan) Kawasaki 45:38.999
10. Loris Capirossi (Italy) Ducati 45:41.497

Selected others:
15. Shane Byrne (Britain) Proton KR 46:39.630