Lochte touched in a time of one minute 54.98 seconds, almost a second slower than the world record of 1:54.00 he set to win the gold in 2011. Kosuke Hagino of Japan was second in 1:56.29 and Thiago Pereira of Brazil third in 1:56.30.
Lochte is the second man only after compatriot Michael Phelps to win a treble of 200 medley world titles.
Phelps took gold in the event in 2003, 2005 and 2007 and beat Lochte into second place to win the Olympic title in London last year.
Australian James Magnussen won a second consecutive gold in the men's 100 metres freestyle at the world championships.
The man known as "the missile" clocked 47.71 seconds, with Jimmy Feigen of the United States taking silver in 47.82 and his compatriot Nathan Adrian, the Olympic champion, bronze in 47.84.
The only men to have previously won two straight 100 freestyle world titles are American Matt Biondi, Alexander Popov of Russia and Italian Filippo Magnini.
Adrian pipped Magnussen into second place by one hundredth of a second to win Olympic gold in London last year.
- Sports & Recreation
- Michael Phelps
- James Magnussen
- Thiago Pereira