Michael Phelps of the U.S. competes during the Men's 200m Butterfly Final in the 13th FINA World Championships in Rome, Italy, July 29, 2009. [Xinhua]

American Michael Phelps won the men's 200m butterfly gold medal in a world record time of one minute 51.51 seconds at the world swimming championships on Wednesday.

Phelps bettered the world mark of 1:52.03 he set in winning Olympic gold on August 13, 2008.

Poland's Pawel Korzeniowski finished second in 1:53.23, beating Japan's Takeshi Matsuda on the final lap.

Matsuda took the bronze in 1:53.32.