- The suspect was arrested in the (coastal city) of Mombasa.
He is now in custody and he was arrested while on the run, George Kinoti, head of Kenya's criminal police, told the AFP news agency.
Agnes Tirop, 25, was found dead on Wednesday in the village of Iten in western Kenya.
When the Kenyan police arrived at Tirop's home, she was lying in her bed with a stab wound to the neck.
- When we got to Tirop's house, we found her in a bed and there was a pool of blood on the floor, says Tom Makori, head of the local police, to the channel NTV Kenya Television.
World record
Just a month ago, Agnes Tirop set a world record for ten kilometers of road with a time of 30.01 in the German Herzogenaurach.
This summer, she finished fourth in the 5,000 meters at the Olympics in Tokyo.
She also has bronze from the WC 2017 in London and bronze from the WC 2019 in Doha.
Both at a distance of 10,000 meters.
"I urge our police to track down and arrest those responsible for the assassination of Agnes Tirop," Kenyan President Uhuru Kenyatta said in a statement after the act.