Munywoki clocked a time of 2:10.07 to beat an international field of more than 4,000 competitors on Sunday.
Ethiopia’s Danel Derese finished second, with a time of 2:12.18, and Kenya’s Dickson Kiptoo was third with 2:12.47.
Dariusz Nożyński was the fastest Pole, clocking in at 2:24.52 to finish eighth overall.
Meanwhile, Ethiopia’s Demissie Abera was the fastest woman, setting a race record of 2:28.35, ahead of Poland’s Iwona Bernardelli with 2:32.25, and another Pole Ewa Jagielska with 2:35.45.
Ethiopia’s Demissie Abera was the marathon's fastest woman, setting a race record of 2:28.35. Photo: PAP/Rafał Guz
Two large marathons are held on the streets of Warsaw every year, one sponsored by fuel giant Orlen in April and another named after state insurance company PZU in September.