Murray was selected from a short-list of athletes "who exemplify the Olympic values and uphold the Team GB values", with the final choice being made by a panel headed by Team GB Chef de Mission Mark England.
"To represent your country at the Games is an unbelievable experience, but to lead out Team GB will be an incredible honour, the biggest in sport," Murray said.
"This is my third Olympic Games and it is a very special competition for me. I obviously have great memories of London and I am 100 percent focused on winning here in Rio.
"The privilege of being the flagbearer is a moment I will remember for the rest of my life and will certainly be one of the highlights of my career."
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England said: "The conviction with which Andy spoke to me about the honour of carrying the flag only underlined why he is such an exceptional individual, and absolutely the right choice.
"When I asked Andy to lead our team out it was received with a humility and grace that is befitting of the values of Team GB. It was an emotional moment for him personally, and for this team."
Murray, who secured his third grand slam title when winning Wimbledon this year, is second-favourite to retain his title behind Novak Djokovic, who he beat on grass in the semi-finals four years ago but who reigns supreme on the hard courts of the type to be used in Rio.
The Scot, who will also partner his brother Jamie in the men's doubles in Rio, was instrumental in leading Britain to the Davis Cup title in Belgium last year - the country's first triumph in the team event since 1936.
(Editing by Alison Williams)
