Patrick finished 5.8594 seconds ahead of pole-sitter Helio Castroneves on the 1.5-mile Twin Ring Motegi oval after leader Scott Dixon pitted with five laps left and Dan Wheldon and Tony Kanaan came in a lap later.
"It's a long time coming. Finally," Patrick said. "It was a fuel strategy race, but my team called it perfectly for me. I knew I was on the same strategy as Helio and when I passed him for the lead, I couldn't believe it. This is fabulous."
The 26-year-old Patrick won in her 50th career IndyCar start, taking the lead from Castroneves on the 198th lap in the 200-lap race.
"I think Danica is such a fantastic person and I'm thrilled for her that the monkey is finally off of her back," said Michael Andretti, co-owner of Andretti Green Racing. "We have all believed in her and she proved today that she is a winner. Frankly, I think this is the first of many."
Dixon took the lead from Castroneves on the 93rd lap in the race pushed back to Sunday because of wet track conditions Saturday, but gave up the spot to pit for fuel.
"We led for a lot of laps but came up short," Dixon said. "But congratulations to Danica for her first victory."
Patrick, who started from the third row and made her final pit stop on lap 148, stayed close to the leaders throughout the race.
Patrick went from fourth to second place on lap 197 after Wheldon and Kanaan went into the pit on lap 196. She was as low as eighth place on the 189th lap.
"I knew there was a good reason for coming to Japan," Patrick said. "I want to thank my team, the fans and everyone who supported me."
Dixon was third, 10.0559 seconds behind Patrick. Wheldon was fourth, and Kanaan finished fifth.
Castroneves, awarded the pole position after qualifying was rained out Friday, said Patrick ran a great race.
"With five laps to go, I was saving fuel," Castroneves said. "When Danica passed me, I realized she was the leader. She did a great job, passed me fair and square and that shows you how competitive our series is."
Patrick finished a career-best seventh in the season standings last year, and was second in the race at Detroit's Belle Isle.
At the 2005 Indy 500, she nearly won the pole and became the first female driver to lead the race en route to a fourth-place finish. It was the best finish by a woman at Indy, and helped her take rookie of the year honors.
American Danica Patrick of Andretti Green Racing celebrates after winning Bridgestone Indy Japan 300 mile auto race on the 1.5-mile oval track at Twin Ring Motegi in Motegi, northeast of Tokyo, Sunday, April 20, 2008.
http://accesswdun.com/article/2008/4/209184