The winner of 14 Olympic gold medals, Phelps will compete in four individual events, 200 meters freestyle, 100 and 200 butterfly and 200 individual medley, and up to three relays.
Ryan Lochte, Phelps' great rival, will also swim in four individual events, 200 meters free, 200 backstroke, 200 and 400 individual medley.
The women's team will be led Natalie Coughlin, winner of six medals at the 2008 Beijing Games while four-time Olympian Amanda Beard returns to action after having a baby.
Teresa Crippen, whose brother Fran died competing in an open water race in the Middle East last year, and Jessica Hardy, who removed herself from the 2008 U.S. Olympic team after testing positive for a banned substance, will also be part of the 42 member squad.
The world championships are scheduled to run from July 19-31 in Shanghai.