The Olympic Council of Ireland confirmed last night that the boxer, who's from Clonmel, was no longer contesting the provisional suspension imposed on him for failing a doping test.
Michael O'Reilly admitted in a statement to unintentionally taking a supplement which may have contained a banned substance.
In the statement, he says was given the “supplement by someone unrelated to his team or association”.
The 23-year-old apologised to his team-mates, supporters and sports organisations.
It follows six days of uncertainty after it was revealed last week that he had tested positive for a prohibited substance.
The test was carried out before O’Reilly or the team travelled to Brazil.
Ireland Boxing Coach Eddie Bolger gave his reaction to O'Reilly's exit from the Games.
The Irish Athletic Boxing Association said they are very disappointed that Michael O'Reilly may have taken any supplement without consulting their High Performance Support Team and confirmed that the boxer has left the Olympic Village.
Arrangements are being made for him to return to Ireland.
