At the 2016 Summer Olympics, Sun won the 200 metre freestyle with a time of 1:44.65, finishing 0.55 seconds ahead of runner-up Chad le Clos. It was Sun's first major international title in this event, and he became the first Chinese athlete to win a gold medal in this event. He won a silver medal in the 400 metre freestyle with a time of 3:41.68, finishing 0.13 seconds behind Mack Horton of Australia. Sun finished 16th in the qualifying heats of the 1500 metre freestyle, clocking in at 15:01.97. With his 200-metre freestyle gold medal and his 400 and 1500 metre freestyle gold medals from the 2012 Summer Olympics, Sun became the first swimmer in history to win Olympic gold medals in the 200, 400, and 1500 metre freestyle events.