Laviai Nielsen is a British sprinter. She competed in the women’s 400 meters at the 2017 European Athletics Indoor Championships, finishing in fourth place in the final.
Laviai Nielsen was born on March 13, 1996, in Leytonstone, East London. She has an identical twin sister, Lina Nielsen, who is also an international athlete in the same events. Laviai Nielsen was initially a middle-distance runner, but in 2013 she and her twin sister were approached at an event and persuaded to change specialism to the 400 meters. Laviai proceeded to reduce her 400 m personal best by 2 seconds within 2 months, and a further four seconds by the following season.
The breakthrough year of Laviai Nielsen came in 2015 when she won gold in the 400 meters at the 2015 European Junior Championships in Sweden. She topped this off by running the final leg for the winning 4 x 400 meters relay team, with her sister Lina running the second leg. Laviai Nielsen also lowered her personal best to 52.25 s, the best time in 2015 for an under-20 athlete, and the third-fastest performance of all time for a British junior.
In February 2017, she recorded a personal best of 51.90 s at an indoor meet in Birmingham. In the summer, she reached the final of the 400 meters at the 2017 European Indoor Championships in Belgrade, finishing fourth to miss out on a bronze medal by just 0.27 seconds. On the final day of the championships, she ran the anchor leg of the 4 x 400-meter relay, winning the silver medal behind a strong Polish team. She became a double British champion when successfully defending her 400 meters event at the 2020 British Athletics Championships in a time of 51.72 secs.