Sifan Hassan, who is 10,000m and 1500m world champion, pulled away from Kenyan marathon world record holder Kosgei at the end of the one-hour race.
“I’m very happy. When I started, I didn’t feel good,” Hassan said. “But after I found every single minute very easy.
“It was a very strong race and I’m so happy. I never thought I was going to run so far.”
Four-time Olympic champion Mo Farah will try to break the men’s one-hour world record on his return to the track at the same meeting later on Friday.