Swimming at the 2007 World Aquatics Championships – Men's 400 metre individual medley

The men's 400 metre individual medley (IM) at the 2007 World Aquatics Championships took place on 1 April (heats and final) at the Rod Laver Arena in Melbourne, Australia. As the event was over 400 meters in length, no semifinals were held in it and the top 8 swimmers from the preliminary heats advance directly to the single final heat. 50 swimmers were entered in the event, of which 49 swam.

Existing records at the start of the event were:
 * World record (WR): 4:08.26, Michael Phelps (USA), August 17, 2004 in Athens, Greece
 * Championship record (CR): 4:09.09, Michael Phelps (USA), Barcelona, Spain (July 27, 2003)