The 2003 SummerSlam was the 16th annual SummerSlam professional wrestling pay-per-view (PPV) event produced by World Wrestling Entertainment (WWE). It was held for wrestlers from the promotion's Raw and SmackDown! brand divisions. The event took place August 24, 2003, at the America West Arena in Phoenix, Arizona.

Seven professional wrestling matches were set on the event's supercard, a scheduling of multiple high-level matches. The first main event was an Elimination Chamber match, in which World Heavyweight Champion Triple H defeated Chris Jericho, Goldberg, Kevin Nash, Randy Orton, and Shawn Michaels to retain his championship. In the other main event, defending WWE Champion Kurt Angle defeated Brock Lesnar in a standard wrestling match. The undercard included Kane defeating Rob Van Dam in a No Holds Barred match, and Eddie Guerrero defending his United States Championship against Chris Benoit, Rhyno, and Tajiri. There was also a match that occurred on the Sunday Night Heat pre-show.

The event marked the second time the Elimination Chamber format was used by WWE; the first was at Survivor Series 2002. SummerSlam (2003) grossed over $715,000 ticket sales from an attendance of 16,113 and received about 415,000 pay-per-view buys, more than the following year's event. This event helped WWE increase its pay-per-view revenue by $6.2 million from the previous year. The event was also the final SummerSlam to not feature John Cena until the 2018 event.