Kornelia Lesiewicz (born 14 August 2003)[3] is a Polish athlete sprinter who specializes in the 400 metres.

At the age of 15, Kornelia Lesiewicz finished sixth in the 400 metres at the 2019 European Youth Olympic Festival held in Baku, Azerbaijan.

In August 2020, she broke the 46-year-old national under-18 best in the 400 m in a time of 52.86 seconds at the Irena Szewińska Memorial in Bydgoszcz, Poland.

[5] In 2021, the 17-year-old was a part of national 4×400 m relay team, winning a bronze medal at the European Indoor Championships – where she was the youngest athlete to win a medal, a silver at the World Relays, and a gold at the European Team Championships Super League.

[6] On 16 July, competing against sprinters up to two years her senior, Lesiewicz won a gold medal in the individual event at the European U20 Championships with a time of 52.46 s.[7] She improved by almost half a second to take a silver at the World U20 Championships held in Nairobi, Kenya, finishing behind only Nigeria's Imaobong Nse Uko.