Daiya Seto is a Japanese professional swimmer who specializes in individual medley, butterfly, breaststroke, and freestyle events. He holds the world record in the short course 400-metre individual medley and formerly held the world record in the short course 200-metre butterfly. He won the gold medal in the 400-metre individual medley at the 2012, 2014, 2016, 2018, 2021, and 2022 world short course championships, as well as at the 2013, 2015, and 2019 world long course championships.