The two-time Olympic gold medallist will be participating in his fourth Olympics.
"It’s an incredible honour to represent the United States on this global stage, especially in a moment that can bring the whole world together," James said in a statement.
"For a kid from Akron, this responsibility means everything to not only myself, but to my family, all the kids in my hometown, my teammates, fellow Olympians and so many people across the country with big aspirations.
"Sports have the power to bring us all together, and I’m proud to be a part of this important moment."
His female counterpart, who will also carry the flag on a barge along with boats carrying all other teams down the river Seine in front of 300,000 spectators, will be announced on Tuesday.
James and his flag bearer counterpart were chosen by a vote of fellow Team USA athletes.
