Both men are reigning Olympic champions
Paddy Barnes was one of the first athletes to be told he would be his countries' flag-bearer at the Rio Olympics, but for most countries, they decisions are only being made, days before the tournament begins.
Great Britain and the United States have both picked iconic sportsmen and reigning Olympic champions from their own countries to lead their teams into the Maracana Stadium. Andy Murray and Michael Phelps have both been handed the honour by their respective Olympic bodies.
Murray will be competing in his third Olympic Games, and is already a two-time medalist. In London, he won the men's singles titles and also won a silver medal in the mixed doubles. In Rio he will be hoping to defend his singles title, and will compete with bother Jamie in the men's doubles.
Speaking after being announced, Murray said; "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."
Despite competing in his fifth Olympic Games, Michael Phelps will take part in his first Opening Ceremony on Friday night. The swimmer is the most successful Olympian of all time having won 22 medals including 18 golds.
The 31-year-old is competing in Brazil in only competing in three individual events in Brazil. His previous schedules hampered him from taking part in Opening Ceremonies due to competing the morning after.
“For Sydney, I just wanted to make the team", Phelps said after the announcement. "For Athens, I wanted to win gold for my country. For Beijing, I wanted to do something nobody else had done. In London, I wanted to make history. And now, I want to walk in the Opening Ceremony, take it all in, represent America in the best possible way and make my family proud. This time around, it's about so much more than medals.”
Phelps becomes only the second American and first male to compete in five separate Olympic Games as a swimmer.