The men's 400 metres at the 2004 Summer Olympics as part of the athletics program were held at the Athens Olympic Stadium from August 20 to 23. Sixty-two athletes from 48 nations competed. The event was won by Jeremy Wariner of the United States, the sixth in what would ultimately be 7 consecutive American victories stretching from 1984 to 2008 and the 18th overall title in the event by the United States. The United States swept the podium for the 4th time in the event.
The women's 400 metres at the 2004 Summer Olympics as part of the athletics program were held at the Athens Olympic Stadium from August 21 to 24. The winning margin was 0.14 seconds.
The women's 400 metres at the 2009 World Championships in Athletics was held at the Olympic Stadium on 15, 16 and 18 August. The world-leader prior to the competition, Sanya Richards, was regarded as the favourite in the event, although her previous failure to convert circuit dominance to major championship success raised some doubts. Reigning Olympic and world champion Christine Ohuruogu entered the championships as only the 25th fastest in the world that year, although a low-key run up also preceded her previous victories. Jamaicans Shericka Williams and Novlene Williams-Mills were predicted as possible medallists, while Russian Antonina Krivoshapka held the second fastest time in the world prior to the tournament.
The Women's 400 metres at the 2011 World Championships in Athletics was held at the Daegu Stadium on August 27, 28 and 29.
The women's 400 metres at the 2013 World Championships in Athletics was held at the Luzhniki Stadium on 10–12 August.
The men's 400 metres event at the 2016 Summer Olympics took place between 12 and 14 August at the Olympic Stadium. Fifty-three athletes from 35 nations competed. The event was won by 0.73 seconds by Wayde van Niekerk of South Africa, who broke the world record and won the nation's second gold medal in the men's 400 metres. Kirani James of Grenada and LaShawn Merritt of the United States became the sixth and seventh men to win two medals in the event, but Michael Johnson remained the only man with two gold medals.
Natalia Kaczmarek is a Polish sprinter who specialises in the 400 metres. She is the 2024 European champion as well as the European silver medalist from 2022. Kaczmarek earned several global medals as part of 4 x 400 m relays, including gold in the mixed event and silver in the women's event at the 2020 Tokyo Olympics.
The women's 400 metres hurdles event at the 2020 Summer Olympics took place between 31 July and 4 August 2021 at the Japan National Stadium. 39 athletes from 25 nations competed.
The mixed 4 × 400 metres relay event at the 2020 Summer Olympics took place on 30 and 31 July 2021 at the Japan National Stadium. There were 16 competing relay teams, with each team having 4 members. It was the first mixed-gender relay in athletics held at the Olympic Games, as part of a larger focus on gender equality by the International Olympic Committee.
Femke Bol is a Dutch track and field athlete who competes in hurdling and sprinting. She specialises in the 400 metres hurdles, where she is the 2023 World Champion, and in the 400 metres, where she is the 2024 World Indoor Champion and the short track world record holder. In the 4 × 400 metres relay, she is the 2023 World Champion and the 2024 World Indoor Champion with the Dutch women's team.
Lieke Klaver is a Dutch track and field athlete who competes in sprinting. She specializes in the 200 metres and in the 400 metres. In the 4 × 400 metres relay, she is the 2023 World Champion and the 2024 World Indoor Champion with the Dutch women's team.
The women's 400 metres event at the 2021 European Athletics Indoor Championships was held on 5 March 2021 at 11:22 (heats) and at 19:33 (semi-finals), and on 6 March 2021 at 20:25 (final) local time.
Sharlene Mawdsley is an Irish athlete who specialises in the 400 meters and other sprint events.
The women's 4 × 400 metres relay at the 2022 World Athletics Indoor Championships took place on 20 March 2022.
The women's 400 metres hurdles at the 2022 World Athletics Championships was held at the Hayward Field in Eugene from 19 to 22 July 2022. It was won by Sydney McLaughlin in a world record time of 50.68 seconds. The winning margin was 1.59 seconds which as of 2024 stands as the greatest winning margin for the women's 400 metres hurdles at these championships.
The women's 400 metres hurdles at the 2022 European Athletics Championships took place in three rounds at the Olympiastadion in Munich, Germany, from 17 to 19 August 2022.
The women's 400 metres at the 2023 World Athletics Championships was held at the National Athletics Centre in Budapest, Hungary from 20 to 23 August 2023. The winning margin was 0.81 seconds which as of 2024 is the only time the women's 400 metres has been won by more than 0.7 seconds at these championships.
The women's 400 metres hurdles at the 2023 World Athletics Championships was held at the National Athletics Centre in Budapest, Hungary from 21 to 24 August 2023. The final was won by the Dutchwoman Femke Bol in a time of 51.70 s, ahead the American Shamier Little in second place and the Jamaican Rushell Clayton in third place.
The women's 400 metres at the 2024 World Athletics Indoor Championships took place in the Commonwealth Arena in Glasgow, Scotland, United Kingdom. The four heats and two semi-finals were held on 1 March 2024. The final was held on 2 March 2024, where Femke Bol won the gold medal finishing in a new short track world record time of 49.17 s, followed by Lieke Klaver in 50.16 s and Alexis Holmes in 50.24 s.
The women's 400 metres hurdles at the 2024 European Athletics Championships took place in three rounds at the Stadio Olimpico in Rome, Italy, from 9 to 11 June 2024. This was the sixteenth time that the women's 400 metres hurdles was contested at the European Athletics Championships. A total of 37 athletes qualified for the event by entry standard, ranking, or wild card. The startlists contained 35 athletes from 21 countries.
