The 400 metres, or 400 metre dash, is a common sprinting event in track and field competitions. It has been featured in the athletics programme at the Summer Olympics since 1896 (1964 for women). On a standard outdoor running track, it is exactly one lap around the track. Runners start in staggered positions and race in separate lanes for the entire course. In many countries, athletes previously competed in the 440 yard dash (402.336 m)—also referred to as the 'quarter-mile'—instead of the 400 m, though this distance is now obsolete. An athlete who competes in the 400 m may still be referred to as 'quarter-miler'.

Maximum sprint speed capability is a significant contributing factor to success in the event, but athletes also require substantial speed-endurance and the ability to cope well with high amounts of lactic acid to sustain a fast speed over a whole lap. Whilst considered to be predominantly an anaerobic event, there is some aerobic involvement and the degree of aerobic training required for 400 metre athletes is open to debate.^{[citation needed]}

Yohan Blake (born December 26, 1989) is a Jamaican sprinter and the current 100 metre World Champion. He holds the national junior record for the 100 metres, and is the youngest sprinter to have broken the 10-second barrier (at 19 years, 196 days). Blake's personal best of 9.82 seconds makes him the fourth fastest Jamaican runner, after Nesta Carter, Asafa Powell and Usain Bolt. His fastest run under any conditions is 9.80 seconds in May 2011 in Kingston, but the wind assistance (+2.2 m/s) was over the legal limit. He is coached by Glen Mills, and is training partners with Bolt and Daniel Bailey. On September 16, 2011 in Brussels, Belgium, he won in a time of 19.26 seconds, the second fastest 200 m ever.

Born in St. James, Jamaica, Blake is the son of Veda and Shirley Blake. He attended St. Jago High School in Spanish Town.

Blake set the fastest time by a Jamaican junior sprinter over 100 m with 10.11 seconds. The record was set at the 2007 CARIFTA Games held in the Turks and Caicos islands where he also led his team to gold in the 4 × 100 metres relay. At this occasion, he was awarded the Austin Sealy Trophy for the most outstanding athlete of the 2007 CARIFTA Games.