The 63-year-old will be the main presenter of the Summer Games for a seventh time, the most in United States television history.

He has also been the host of four Winter Olympics.

It will be Costas' 12th appearance at the Olympics having been the late night host for NBC at the 1988 Olympics in Seoul. 

London 2012 was seen by 217 million viewers, making it the most watched television event in American history. 

"For a quarter-century, Bob has been NBC's pilot of primetime at the Olympics, and over that span, the scope of our coverage has constantly evolved, with Rio set to become the most live event in US television history," said Jim Bell, executive producer, NBC Olympics.

"Given his vast experience and uncanny expertise, simply put there is no one better than Bob to tell the stories of the athletes, take our viewers inside the world's biggest sports event, and introduce them to one of the most spectacular cities on the planet."

Costas, who also serves as host of Football Night in America each Sunday, has won 26 Emmy Awards, the most of any sports broadcaster. 

"The Olympics are a unique television event," Costas said.

"They involve classic sports coverage, of course, but also many elements of storytelling and travelogue aspects that are not as much a part of the typical sports broadcast.

"In a way, the Olympics are a three-week mini-series which, if done well, should bring viewers not only memorable athletic performances, but a sense of the host city and country, and an appreciation of what is a truly global gathering."