The 2008 SummerSlam was the 21st 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, SmackDown, and ECW brand divisions. The event took place on August 17, 2008, at Conseco Fieldhouse in Indianapolis, Indiana. It was the first PPV of the PG Era, although nobody noticed it at the time because there were still two Ruthless Aggression rivalries still going on, one of which ended at this event. The transition into the PG Era was more noticeable on the next episode of Monday Night Raw. It was also the first SummerSlam PPV broadcast in high definition.

Seven professional wrestling matches were featured on the event's card. The event featured a supercard, a scheduling of more than one main event. The first, featuring wrestlers from the SmackDown brand, saw The Undertaker defeat Edge in a Hell in a Cell match, a match that saw both men fight in a ring surrounded by a roofed steel cell. The other main event featured wrestlers from the Raw brand, in which Batista defeated John Cena in a standard wrestling match. Three featured bouts were scheduled on the undercard. In a standard match from SmackDown, WWE Champion Triple H defeated challenger The Great Khali to retain his title. Another was a standard match involving wrestlers the Raw brand, where World Heavyweight Champion CM Punk defeated challenger John "Bradshaw" Layfield (JBL) to retain his title. The ECW brand's sole contribution to the card saw Matt Hardy defeat ECW Champion Mark Henry by disqualification, as a result of WWE regulations, Hardy did not win the title as they can only be won via pinfall or submission.