The men's 400 metres at the 2015 World Championships in Athletics was held at the Beijing National Stadium on 23, 24 and 26 August.

The 2015 IAAF World Championships, the fifteenth edition of the IAAF World Championships, were held from 22 to 30 August at the National Stadium in Beijing, China. Forty-three nations won medals, 144 of which were awarded. Kenya topped the medal table for the first time, with 7 gold, 6 silver and 3 bronze medals. The United States won 18 medals, six gold, six silver and six bronze, which was the highest tally. Host nation China, finished 11th on the medals table, while Russia finished ninth.