The 24-year-old Kirui, who won Boston marathon in April, crossed the line in 2:08:27 more than one minute ahead of Rio Olympics 10000m silver medalist Tamirat Tola, who came in second in 2:09:49.
Alphonce Feliz Simbu of Tanzania, 5th place finisher at last year's Olympics, claimed bronze medal at World Athletics Championships on Sunday with a time of 2:09:51
Great Britain's Callum Hawkins was best European marathoner at these championships as he placed in 4th with a new personal best time of time of 2:10:17. Another European athlete to make top 10 was Italy's Daniele Meucci who set a personal best of 2:10:56 to finish in 6th position.
1. Geoffrey Kipkorir KIRUI KEN 2:08:27 SB
2. Tamirat TOLA ETH 2:09:49
3. Alphonce Felix SIMBU TAN 2:09:51
4. Callum HAWKINS GBR 2:10:17 PB
5. Gideon Kipkemoi KIPKETER KEN 2:10:56
6. Daniele MEUCCI ITA 2:10:56 PB
7. Yohanes GHEBREGERGIS ERI 2:12:07
8. Daniel Kinyua WANJIRU KEN 2:12:16
9. Yuki KAWAUCHI JPN 2:12:19
10. Kentaro NAKAMOTO JPN 2:12:41