For the 2005 season, Wheldon again drove for AGR. He started from eleventh to lead a race-high 158 of 200 laps of the Homestead–Miami Speedway season-opener to win. After that, Wheldon went on to win consecutive races at the Grand Prix of St. Petersburg (his first road course series win), and the Indy Japan 300 for the second successive year. His season highlight was the Indianapolis 500 where he exchanged the lead with Danica Patrick until she slowed due to a lack of fuel. Wheldon made the race-victory overtake with seven laps to go to become the first British driver to win the event since Graham Hill in 1966. He continued to drive consistently in the top six in the next seven races. At Pikes Peak International Raceway, Wheldon took his fifth win of the season (after leading 67 laps) to equal Sam Hornish Jr.'s 2002 record of five victories during a season. Two races later, at Chicagoland Speedway, he led a race-high 88 laps to surpass Hornish's series record with his sixth win of the year. Wheldon won the championship before starting the season's penultimate round by setting a single practice lap of Watkins Glen International. Since the last place finisher scored 12 points, his 102-point lead clinched the title with one race remaining. With a sixth-place finish at the season-closing California Speedway round, Wheldon won the championship with 628 points. He was awarded the 2005 Autosport British Competition Driver of the Year.