At the 2008 Summer Olympics in Beijing, China, Peirsol won gold in the 100-meter backstroke and the 4×100-meter medley relay. He also won silver in the 200-meter backstroke. In his first event, the 100-meter backstroke, Peirsol was the heavy favorite for gold, with him being the world-record holder and the defending Olympic champion. For the final of the 100-meter backstroke, Peirsol was swimming in lane two, having qualified fifth in the semi-finals. At the first 50-meters in the 100-meter backstroke final, Peirsol was in second place behind Liam Tancock, who took it out in 25.11. Peirsol was 0.54 s behind Tancock at the turn. However, after the turn, Peirsol overtook Tancock, who eventually placed sixth, and won the gold. Peirsol's final time of 52.54 was a new world record, bettering his previous mark of 52.89 set last month. After the race, Peirsol said, "I'm a little bit excited, a little bit relieved, absolutely elated." In his second event, the 200-meter backstroke, Peirsol placed second to Ryan Lochte 1:54.33 to 1:53.94. In winning the gold, Lochte broke the world record tie he and Peirsol shared in the 200-meter backstroke. In his last event, the 4×100-meter medley relay, Peirsol combined with Brendan Hansen, Michael Phelps, and Jason Lezak to win gold in a world record time of 3:29.34, lowering the old mark of 3:30.68 set four years ago in Athens.