Earlier in his career Max Biaggi was considered Rossi's main rival. At one time his website didn't even have Max's name; instead a glaring "XXX XXXXXX" was placed wherever his name should have appeared. Although they hadn't even raced against each other until 2000, the rivalry between the two had been growing since the mid-'90s. The rivalry has started to die down over recent years due to Rossi 's consecutive World Championships and Biaggi's struggle to find support and a consistent rhythm with his races. Biaggi looked to improve on recent results with a ride with Honda's factory team in 2005. However, he was off the team and unemployed once the 2006 season rolled around.

In his autobiography "What If I Had Never Tried It", Rossi makes a number of claims about the reasons for his rivalry with Biaggi, and some of the incidents which led to its escalation. The rivaly was also featured in the 2003 documentary film, Faster.

During one incident at Suzuka in 2001, Rossi alleges that Biaggi elbowed him on the straightway at 220 km/h to prevent him from overtaking.[citation needed] This caused Rossi to lose a lot of time and drop several places, but he managed to make up the time and eventually overtook Biaggi to win the race. As he overtook Biaggi, he took his left hand from the handlebars of his bike and gave Biaggi the middle-finger.[11]

By the time the 2001 season had moved to Barcelona, the animosity from Suzuka had festered.[citation needed] After the race (which Rossi won), the pair got into a fist-fight before the podium presentation. The tension was evident in the press conference, although the media hadn't yet found out what had happened. The Dorna officials took Rossi and Biaggi aside immediately after the press conference and ordered them not to talk about the incident, and to play it down.[citation needed] Neither rider was sanctioned for the incident.

At the next Grand Prix in Assen, Honda organized a press conference to put the events of Barcelona behind them. Rossi and Biaggi shook hands in front of the media, and that effectively ended the feud. After that, although they have had run-ins on track, the media frenzy surrounding them and any incidents off-track calmed down.[citation needed]

Rossi's main rival in the 2003/2004/2005 seasons was Sete Gibernau, riding with Team Gresini's Movistar Honda team on a satellite RC211V in 2004 and then on an all but in name factory RC211V, which Gibernau helped to develop, in 2005. Initially they were quite friendly in the paddock and off - Gibernau partied on occasions with Rossi at the Italian's Ibiza villa - but a souring in their relationship began in the 2004 season and culminated in the "Qatar Incident" that same season when Rossi's team was penalized for "cleaning" his grid position to aid in traction, along with Honda Pons' Max Biaggi, and both riders were subsequently forced to start from the back of the grid. A number of teams, including Gibernau's Team Gresini and the official Repsol Honda factory team, appealed successfully to race direction for Rossi to be sanctioned. Rossi and his chief mechanic, Jeremy Burgess, insisted that they were doing nothing more than what many others had done before when faced with a dirty track and Rossi accused Gibernau of being behind the move to appeal for a sanction, something the Spaniard categorically denied.[citation needed]

Since then the two have not spoken and Rossi seemed to resolve to use the incident to apply psychological pressure on Gibernau. He is said to have sworn that after the Qatar race, which Gibernau won while Rossi crashed out after rising to 6th position, he would do everything to make sure that Gibernau never stood on the highest step of the podium again.[citation needed] Gibernau retired from Grand Prix racing after an unsuccessful, injury blighted 2006 season with Ducati and he never won another race after Qatar, prompting some in the Spanish and Italian motorcycle racing media to explain this fact by way of reference to the "Qatar curse."[citation needed] But he returned at the end of 2008, after tests on the 2008 Ducati convinced him that he could still be competitive in MotoGP, and signed to ride a Ducati in 2009.

In 2007, Casey Stoner emerged as a rival for Rossi. Coupled with a Ducati, the young Australian won the first race of the year, followed by many more victories resulting in his claiming of the 2007 MotoGP World Championship title. Stoner's and Rossi's rivalry came to a dramatic climax at Laguna Seca in 2008. After numerous position changes, Rossi attempted to overtake Stoner through the corkscrew. This bold move caused Rossi to run wide into the gravel, and his rejoining the track came close to causing a collision between the two riders. A few laps later Stoner went into the gravel on the slow entry into turn 11, yet picked up the bike to finish second while Rossi took the win. After this, Casey Stoner made the comment 'I have lost respect for one of the greatest riders in history'. For the comment, Stoner apologized to Rossi at the next race.[12]