Marco Michael Andretti was born in Nazareth, Pennsylvania, he drives the number 26 car for Andretti-Green Racing in the Indy Racing League. He is the son of 1991 IndyCar World Series champion Michael Andretti and the grandson of racing legend Mario Andretti. Andretti finished second in the 2006 Indianapolis 500 in the second closest finish in the race's history.
Barely out of high school, he ran in the Star Mazda series in 2005 after two years in Skip Barber national competition, before moving up to the Indy Pro Series. He won three races (St. Petersburg, Indianapolis (road course), and Sonoma) and finished 10th in points despite only starting half the races.
Motorsports journalist Gordon Kirby suggested at the Champ Car finale in Mexico City that the youngest Andretti would be replacing Dan Wheldon in his number 26 Jim Beam Dallara-Honda for 2006 with Michael Andretti coming out of retirement to run a fifth car for his Andretti Green Racing team at the Indianapolis 500. Though a novel proposition to some, it was later confirmed in a December 15 press conference that he would move up to the Indy Racing League full time as the youngest driver in series history and would trade sponsors (New York Stock Exchange and Motorola) with Dario Franchitti as Andretti is not old enough to run an alcohol-sponsored car. His father, Michael Andretti, came out of retirement to run a fifth car for the Indianapolis 500.
In his rookie start on March 26, 2006 at Homestead-Miami Speedway in the number 26 New York Stock Exchange Dallara-Honda, Andretti started in 13th place but made two mistakes. At the start of the race he passed too early. He then launched hard from the pits on his first stop causing a drivetrain failure. He finished near the back.
With his Rookie of the Year performance in May, he became the third Andretti to finish in the top five in his first "500" appearance, joining his father Michael (5th in 1984) and his grandfather Mario (3rd in 1965). He came within 5 feet of winning it, but Sam Hornish, Jr. passed him in the final 300 feet of the race.
On August 27, 2006, Marco Andretti became the youngest winner of a major open-wheel racing event as he scored his first career Indy Racing League victory at Infineon Raceway in Sonoma, California. His win established him as the 2006 Bombardier Rookie of the Year.
Honda Racing F1 announced in December, 2006 that Andretti would be presented with an opportunity to test their Formula One car. On December 15, Andretti made his debut in a Formula One car at Jerez in Spain. Although he was over two seconds slower than fellow Honda tester Christian Klien, Honda sporting director Gil de Ferran commented that he had done a "good job".
Andretti said that he had greatly enjoyed the test but also told reporters that he wishes to enter Formula One only after he has won the Indy 500.
On February 7 and February 8, 2007 Marco participated in a second Honda Racing F1 test for two days in Jerez, Spain. His (unofficial) fastest lap of the day on February 7 was less than 1.5 seconds slower than team driver Jenson Button's fastest time. His (unofficial) fastest time on February 8 (in rainy/changing conditions) was less than one second slower than that of the 2005 and 2006 Formula One World Drivers' Champion Fernando Alonso's fastest lap.