The men's 400 metres at the 2019 World Athletics Championships was held at the Khalifa International Stadium in Doha on 1, 2 and 4 October 2019.

Fredrick Lee Kerley is an American professional track and field sprinter who started his career competing in the 400 meters until 2020, when he transitioned to the 100 meters and 200 meters. He has earned several medals at the World Championships in the 400 m and 4 × 400 m relay including an individual bronze and a relay gold at the 2019 edition. Kerley claimed 100 m gold in the 2022 edition.