And we have a new WR
Kosgei has finished in the top two in eight of the nine marathons that she has run in her career. She came second at the 2016 Lisbon Marathon behind Sarah Chepchirchir, in a personal best time of 2:24:45. Her time was faster than the previous course record. In 2017, Kosgei won the Bogotá Half Marathon, and came third at the Copenhagen Half Marathon. She came second in the 2017 Chicago Marathon in a personal best time of 2:20:22. Her time was the sixth fastest ever time at the Chicago Marathon. Weeks later, she won the Honolulu Marathon, beating the course record by over five minutes. In 2018, Kosgei came second in the London Marathon behind Vivian Cheruiyot. After injuring herself during the Bogotá Marathon, Kosgei decided to run the Great North Run, in order to practice ahead of the 2018 Chicago Marathon. She finished the event second, behind Cheruiyot. Kosgei later won the Chicago Marathon, after breaking away from a group of two other Kenyans and three Ethiopians after between 30–35 kilometres (19–22 mi) of the race. She set a personal best time of 2:18:35. During 2018, Kosgei also won a cross country event in Eldoret, Kenya, and the Kalya Half Marathon in Kapenguria, Kenya.
Kosgei won the 2019 London Marathon, becoming the youngest woman ever to win the event. This is the third best time ever in London after Paula Radcliffe in 2005 with 2:17:42 and Mary Keitany 2017 with the world record 2:17:01. At the 2019 Great North Run, Kosgei won in a course-record time of 1:04.28, 23 seconds faster than the previous half marathon world record set by Joyciline Jepkosgei.
She won the 2019 Chicago Marathon on 13 October 2019 in a world record time of 2:14:04 an improvement of her personal best by more than 4 minutes.