Thomas Allen Shields is an American competitive swimmer. He is a two-time Olympian and the current American record-holder in the short course 50-meter butterfly and 200-meter butterfly. At the 2016 Summer Olympics, he won a gold medal in the 4×100-meter medley relay, 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 seconds.

The 2016 USA Swimming Olympic trials were held for the third straight quadrennial at CenturyLink Center Omaha in Omaha, Nebraska from June 26 to July 3, 2016. Those qualifying competed for the United States in Swimming at the 2016 Summer Olympics in Rio de Janeiro, Brazil.