2003 NASCAR Winston Cup Series (Start Your Engines!)

The 2003 NASCAR Winston Cup Series was the 55th season of professional stock car racing in the United States and the 32nd modern-era Cup series season.

This was the final year for Winston being the title sponsor of the Cup Series. Winston had been the title sponsor for NASCAR since 1971. After 33 years, Winston decided not to renew its sponsorship. NASCAR went to work to find a sponsor immediately, and on June 19, 2003, NASCAR announced that the telecommunications firm Nextel would be the new title sponsor of the Cup Series starting in 2004. This was also the final season for Unocal 76 Brand as the official fuel for NASCAR. Unocal had been the official fuel since the sport's inception in 1948. Sunoco would replace Unocal 76 as the official fuel of NASCAR.

Technical changes
2003 saw the second major change to the SAFER Car body, the first since 1999. Chevrolet and Ford had been making massive changes to the Monte Carlo and Taurus bodies, respectively, on a weekly basis in an attempt to match the dominant Dodge Intrepids. For 2003, NASCAR mandated the use of a common template for rooflines and rear decklids to rein the two makes in.

Ford Motor Company decided to rationalize the amount of makes they had in NASCAR before the end of 2002, and decided to focus all their efforts on their namesake marquee. Mercury and Lincoln, as a result, exited the sport, with Mercury going defunct in 2011 during the Great Recession, while Lincoln is still in business, but is very unlikely to return to NASCAR due to the Continental, their last passenger car, being discontinued with the rising popularity of SUVs.

2003 also saw Pontiac bowing out of NASCAR, again so General Motors could focus their resources on a single marquee to combat Dodge, this being Chevrolet. Pontiac would eventually return in 2015 to combat Toyota.