As he took the silver medal, Feyisa Lilesa crossed his arms above – a gesture made by the Oromo people who have suffered brutal police crackdowns.
Lilesa is from Oromia, home to most of Ethiopia’s 35 million Oromo people.
He repeated the protest gesture later at a press conference, saying his life would be in danger if he returned home.
Human rights groups say that Ethiopian security forces have killed hundreds of people in recent weeks as they crack down on anti-government protests.
Explaining his actions, Lilesa said: “The Ethiopian government are killing the Oromo people and taking their land and resources so the Oromo people are protesting and I support the protest as I am Oromo.
“The Ethiopian government is killing my people so I stand with all protests anywhere as Oromo is my tribe. My relatives are in prison and if they talk about democratic rights they are killed. I raised my hands to support with the Oromo protest.”
The marathon runner said that he might be killed if he returned.
“If not kill me, they will put me in prison,” he said. “I have not decided yet, but maybe I will move to another country.”
Asked if he was worried about being sanctioned by the International Olympic Committee (IOC), he said: “I cannot do anything about that. This was my feeling. I have a big problem in my country, it is very dangerous to make protest in my country.”