Who set the men's 400m world record of 43.03 seconds?

Wayde van Niekerk set the men’s 400-metre world record of 43.03 seconds. The South African ran that time in the Olympic final at the 2016 Rio de Janeiro Games, winning the gold medal from the outside lane.

Van Niekerk’s performance broke the previous world record of 43.18 seconds, set by American Michael Johnson at the 1999 World Championships. It also made van Niekerk the first athlete to run under 43.10 seconds for 400 metres. His time remains one of the defining sprint performances in modern athletics.

The 400 metres is one complete lap of a standard outdoor track, with athletes starting from staggered positions and remaining in their lanes. Although the event is classified as a sprint, it demands unusual endurance as well as explosive speed. Michael Johnson remains a common answer choice because he held the record for 17 years, but van Niekerk surpassed him in 2016. Kirani James and Jeremy Wariner were also elite 400-metre champions, but neither set the 43.03 record.