The men's 400 metres at the 2009 World Championships in Athletics was held at the Olympic Stadium on 18, 19 and 21 August.
Similar to the 2007 World Championships, Jeremy Wariner and LaShawn Merritt were the clear favourites.
A gold or silver medallist outside of these two competitors seemed unlikely; Bahamian Chris Brown, Irishman David Gillick, Frenchman Leslie Djhone and the other two runners from the United States (Gil Roberts and Lionel Larry) were seen to be capable of a bronze at best.
[1] On the first day, Ramon Miller surprised as the fastest qualifier in the heats, scoring a new personal best of 45 seconds.
Tabarie Henry, Djhone and Renny Quow were the next fastest, and African record holder Gary Kikaya was most high-profile casualty of the first round, having been disqualified for a lane infraction.