The 2008 No Mercy was the 11th No Mercy 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 October 5, 2008, at the Rose Garden in Portland, Oregon. It is one of only two WWE pay-per-view events to be held in the state of Oregon, the other being Unforgiven in 2004. No Mercy was replaced by Hell in a Cell in 2009; however, after eight years, No Mercy was reinstated in 2016.

Eight professional wrestling matches were scheduled on the event's card, which featured a supercard, a scheduling of more than one main event. The first featured wrestlers from the Raw brand, in which defending World Heavyweight Champion Chris Jericho defeated Shawn Michaels in a ladder match. The other main event featured wrestlers from the SmackDown brand, in which defending WWE Champion Triple H defeated challenger Jeff Hardy in a standard wrestling match. Three featured bouts were scheduled on the undercard. In a standard wrestling match between wrestlers from the Raw brand, Batista defeated John "Bradshaw" Layfield (JBL) to become the number one contender for the World Heavyweight Championship. The second was a standard match between wrestlers from the SmackDown brand in which the Big Show defeated The Undertaker. The third was the predominant match from the ECW brand, a standard match for the ECW Championship, in which the champion Matt Hardy defeated Mark Henry.

The event had an approximate attendance of 10,000. When the event was released on DVD, it reached a peak position of second on Billboard's Recreational Sports DVD Sales Chart. The event received 261,000 pay-per-view buys, less than the previous year's event. It was also the first No Mercy PPV broadcast in high definition.