Thomas Allen Shields (born July 11, 1991) is an American competitive swimmer. He is a two-time Olympian and the current American record-holder in the 200-meter butterfly. At the 2016 Summer Olympics, Shields won a gold medal in the 4x100-meter medley relay for swimming the butterfly leg of the relay in the prelims. Later the same year he became the first American to swim faster than 44 seconds in the 100-yard butterfly, setting a new American record of 43.84. For the 2020 Summer Olympics, he qualified to swim the 100-meter butterfly.