The 27-year-old Chepkoech, who finished 4th at Rio Olympics in 2016, shaved more than 15 seconds from her own personal best and 8 seconds from the previous World record.
"I am so grateful," said new world record holder Chepkoech.
"I said from the beginning, from the first lap, and I was watching the time, and I knew I was going to break the world record."
The old steeplechase World record belonged to Ruth Jebet, a Kenyan born Bahreini athlete, that failed an out of competition doping test for EPO.