The Kenyan bettered it by 50 seconds.
The marathon also serves as a world championships team selection race for Japanese women.
She made a comeback after a Boston DNF last month.
They are both expected to win again.
Lydia Cheromei of Kenya smashed the course record at the Volkswagen Prague Marathon on Sunday by three minutes, running 2:22:34. Benson
She took nearly three minutes off the course record. Check out these great photos from the race!
Mary Keitany's training partner put forth a solid effort in the Czech capital.
It was the first sub-1 hour half on Czech soil.