Usain Bolt's personal best in the 400 metres is 45.28 seconds, recorded in Kingston, Jamaica, in 2007.
Bolt ran the mark on 5 May 2007 at the Jamaica International Invitational. It remains his official personal best for one complete lap of the track. Although he competed occasionally over 400 metres early in his career, he ultimately concentrated on the 100 and 200 metres, where his speed and long stride produced historic records.
The 45.28 can be overlooked because Bolt's most famous performances came in shorter races. It is also different from a relay split: a relay leg can be timed from a running start, while an individual 400-metre race begins from starting blocks. Bolt's 45.28 is an official individual result.