The 2005 No Mercy was the eighth No Mercy professional wrestling pay-per-view (PPV) event produced by World Wrestling Entertainment (WWE). It was held exclusively for wrestlers from the promotion's SmackDown! brand division. The event took place on October 9, 2005, at the Toyota Center in Houston, Texas. Nine professional wrestling matches were scheduled on the event's card.

Three of the four championships exclusive to the SmackDown! brand were contested for; one was lost while the other two were retained. The main event was a standard wrestling match, in which World Heavyweight Champion Batista defeated challenger Eddie Guerrero to retain his title. This would be Guerrero's final pay-per-view match before his sudden death one month later (coincidentally, the event took place on Guerrero’s 38th birthday). One of the featured preliminary matches was a Casket match between The Ortons (Randy and "Cowboy" Bob) and The Undertaker. The Ortons won the match after placing Undertaker inside the casket and closing it. Another primary preliminary match was a standard match between John "Bradshaw" Layfield (JBL) and Rey Mysterio, which JBL won.

The event received 219,000 pay-per-view buys, which was greater than the 193,000 buys the previous year's event received. The event was claimed to be "unmerciful" by Canadian Online Explorer's professional wrestling section, as they rated none of the matches higher than a five out of ten. When the event was released on DVD, it reached a peak position of fourth on Billboard's DVD sales chart for recreational sports. It remained on the chart for four consecutive weeks.