1999 World Championships in Athletics – Men's 400 metres

These are the official results of the Men's 400 metres event at the 1999 IAAF World Championships in Seville, Spain. There were a total number of 48 participating athletes, with six qualifying heats, four quarter-finals, two semi-finals and the final held on Thursday 26 August 1999 at 8.45 pm. The winning margin was 1.11 seconds which as of May 2024 remains the greatest winning margin in the history of the men's 400 metres at these championships and the only time this race has been won by over one second. It was also a greater winning margin than the men's 5,000 metres in 1999.

Semi-final

 * Held on Tuesday 24 August 1999

Quarter-finals

 * Held on Monday 23 August 1999

Heats

 * Held on Saturday 21 August 1999