Kipchoge, who finished the marathon in 2 hours, 8 minutes and 44 seconds, started with a group of a dozen runners that slowly dropped away
Kenya's Eliud Kipchoge won the men's Olympic marathon with a dominating performance, running alone into the Sambadrome and finishing in two hours, eight minutes and 44 seconds today.
Ethiopia's Feyisa Lilesa claimed the silver medal and American Galen Rupp took the bronze in humid conditions on a rain-slicked course.
Kipchoge, 31, began to split the field after around 30 kilometres, starting with a group of a dozen runners about him that slowly dropped away until he ran the final kilometres alone.
"It was a championship and it was a bit slow so I decided to take over. Maybe it was the rain, maybe not. Everyone wants a medal. I was coming here for gold," said Kipchoge, who has won seven of the eight marathons he has entered, including two London Marathon victories.
In previous Olympic appearances, in 2004 and 2008, he had competed in the 5,000 metres before shifting his focus to the longer distance.
Rupp, 30, also made the transition from a short event but did so at the same Games, having finished fifth in the men's 10,000 metres eight days ago.
"I was emotionally drained after the 10K, but I got it out of the system and decided to have an attacking race," Rupp said. "Maybe this is my best event."
It marked the third straight time a Kenyan had claimed a spot on the Olympic podium, following silver and bronze performances in 2012 and a 2008 gold.
Kipchoge's victory came a week after compatriot Jemima Jelagat Sumgong won gold in the women's marathon, marking the first time both races had been won by the same nation.