Joseph Hunter Armstrong (born January 24, 2001) is an American swimmer. He is the world record holder in the long course 50 meter backstroke. At the 2020 Summer Olympics, he won a gold medal in the 4×100 meter medley relay, swimming backstroke in the prelims, and finished ninth in the 100 meter backstroke. He won a gold medal as part of the 4×100 meter freestyle relay, swimming in the prelims heats, at the 2022 World Aquatics Championships as well as a gold medal in the 4×100 meter mixed medley relay, swimming backstroke in the final, a silver medal each in the 50 meter backstroke and the 4×100 meter medley relay, and a bronze medal in the 100 meter backstroke.