
Phelps, whose record 22 Olympic medals include an astonishing 18 gold, clocked 1min 54.84sec to triumph over Tom Shields and become the first man to make a fifth US Olympic swimming team.
Shields finished in 1:55.81, pushing Phelps all the way.
"Getting on this team was what I wanted to do," said Phelps, who celebrates his 31st birthday on Thursday.
The 200m fly was the event in which a teenaged Phelps set his first world record, and his world mark of 1:51.51 -- set at the tail end of the bodysuit era in 2009 -- still stands.
Regaining the Olympic title he surrendered to Chad le Clos in London in an event he long considered his baby figures to be a strong motivator for Phelps in Rio, although he acknowledged the competition would be fierce.
In addition to le Clos, he can expect a strong challenge from Hungary's Laszlo Cseh and Japan's Daiya Seto and Masato Sakai -- the top three in the world rankings.
Phelps is also chasing Olympic berths in the 100m fly and 200m individual medley -- both events he has won at three consecutive Games.
- AFP