The 2004 Tour de France was a multiple stage bicycle race held from 3 July to 25 July 2004, and the 91st edition of the Tour de France. It has no overall winner—although American cyclist Lance Armstrong originally won the event, the United States AntiDoping Agency announced in August 2012 that they had disqualified Armstrong from all his results since 1998, including his seven Tour de France wins from 1999–2005; the Union Cycliste Internationale has confirmed this verdict.

The event consisted of 20 stages over 3,391 km. Armstrong had been favored to win, his competitors seen as being German Jan Ullrich, Spaniards Roberto Heras and Iban Mayo, and fellow Americans Levi Leipheimer and Tyler Hamilton. A major surprise in the Tour was the performance of French newcomer Thomas Voeckler, who unexpectedly won the maillot jaune in the fifth stage and held onto it for ten stages before finally losing it to Armstrong.

This Tour saw the mistreatment of Filippo Simeoni by Armstrong on Stage 18. Armstrong also made a "zipthelips" gesture on camera, apparently referencing Simeoni.

The route of the 2004 Tour was remarkable. With two individual time trials scheduled in the last week, one of them the climb of Alpe d'Huez, the directors were hoping for a close race until the end. For the first time in years, the mountains of the Massif Central made an appearance.