Nicola Clare Sanders is a former British track and field sprinter. She began her career as a 400 metres hurdles specialist before concentrating on the 400 metres from 2006 onwards. Her 400 metres personal best is 49.65 seconds. She holds the British indoor record with 50.02 seconds, which ranks her as the fifth fastest woman of all-time indoors.

The 400 metres, or 400-meter dash, is a sprint event in track and field competitions. It has been featured in the athletics programme at the Summer Olympics since 1896 for men and since 1964 for women. On a standard outdoor running track, it is 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)—which is a quarter of a mile and was referred to as the "quarter-mile"—instead of the 400 m (437.445 yards), though this distance is now obsolete.