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Following his father, Graziano Rossi, Rossi started racing in Grand Prix in 1996 for Aprilia in the 125cc category and won his first World Championship the following year. From there, he moved up to the 250cc category with Aprilia and won the 250cc World Championship in 1999. He won the 500cc World Championship with Honda in 2001, the MotoGP World Championships (also with Honda) in 2002 and 2003, and continued his streak of back-to-back championships by winning the 2004 and 2005 titles after leaving Honda to join Yamaha, before regaining the title in 2008 and retaining it in 2009. He left Yamaha to join Ducati for the 2011 season.
Rossi is first in all time 500 cc/MotoGP race wins standings, with 79 victories, and second in all time overall wins standings with 105 race wins (behind Giacomo Agostini with 122).
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Rossi won the regional kart championship in 1990. After this he took up minimoto and before the end of 1991 had won numerous regional races.
Rossi continued to race karts and finished fifth at the national kart championships in Parma. Both Valentino and Graziano had started looking at moving into the Italian 100cc series, as well as the corresponding European series, which most likely would have pushed him into the direction of Formula One. However, the high cost of racing karts led to the decision to race minimoto exclusively. Through 1992 and 1993, Valentino continued to learn the ins and outs of minimoto racing.
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Although his first season in the Italian Sport Production Championship was varied, he achieved a pole position in the season's final race at Misano, where he would ultimately finish on the podium. By the second year, Rossi had been provided with a factory Mito by Lusuardi and won the Italian title.
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Rossi had some success in the 1996 World Championship season, failing to finish five of the season's races and crashing several times. Despite this, in August he won his first World Championship Grand Prix at Brno in the Czech Republic on an AGV Aprilia RS125R. He finished the season in ninth position and proceeded to dominate the 125cc World Championship in the following 1997 season, winning 11 of the 15 races.
By 1998, the Aprilia RS250 was reaching its pinnacle and had a team of riders in Valentino Rossi, Loris Capirossi and Tetsuya Harada. The death of two of his friends in a car accident also took a toll.[citation needed] He later concluded the 1998 250cc season in second place, only three points behind Capirossi. In 1999, however, he won the title, collecting 5 pole positions and 9 wins.
Rossi won his first 500cc World Championship in 2001 (winning 11 races) in the final year of that class. In the following year, 500cc two-strokes were still allowed, but 2002 saw the beginning of the 990cc four-stroke Moto GP class, after which the 500cc machines were essentially obsolete. In 2001 Rossi teamed up with American rider Colin Edwards for the Suzuka 8 Hours endurance race aboard a Honda VTR1000SPW. The pair won the race despite Rossi's lack of experience racing superbikes.
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It was more of the same in 2003 for Rossi's rivals when he claimed nine pole positions as well as nine GP wins to claim his third consecutive World Championship. The Australian GP at Phillip Island in 2003 is considered by many observers to be one of Rossi's greatest career moments due to unique circumstances. After being given a 10-second penalty for overtaking during a yellow flag due to a crash by Ducati rider Troy Bayliss, front runner Rossi proceeded to pull away from the rest of the field, eventually finishing more than 15 seconds ahead, more than enough to cancel out the penalty and win the race.
Partnered with increased scepticism that the reason for his success was the dominance of the RC211V rather than Rossi, it was inevitable that Honda and Rossi would part. Mid-season rumours pointed towards a possible move to Ducati, which sent the Italian press into a frenzy; the concept of the great Italian on the great Italian bike seemed too good to be true. Ducati did indeed try to seduce Rossi into riding their MotoGP bike, the Desmosedici, but for numerous reasons Rossi passed the offer up. Critics say that compared to the other manufacturers, Ducati had a significant way to go before being competitive even with Rossi at the helm. This proved to be the truth with Ducati's lacklustre performance in the 2004 season, which had actually been worse than their inaugural year in MotoGP in 2003.