Lomong, one of the Lost Boys of Sudan, won a vote of team captains Wednesday to earn the honor of leading America's contingent into the 90,000-seat Bird's Nest Stadium.
The 1,500-meter track runner will be the flagbearer only 13 months after becoming a U.S. citizen.
"It's more than a dream," Lomong said in an interview with The Associated Press moments after he got the news. "I keep saying, I'm not sure if this is true or not true. I'm making the team and now I'm the first guy coming to the stadium and the whole world will be watching me carry the flag. There are no words to describe it."
He was born in Sudan, separated from his parents at the point of a gun at age 6, and with the help of friends, he escaped confinement and made it to a refugee camp in Kenya. In 2001, he was brought to America as part of a program to relocate lost children from war-torn Sudan.
Earlier this week, the 23-year-old Lomong said he was mounting a campaign to be nominated by the track and field team for the flagbearer's position. He said the honor would be memorable, but he also was thrilled to be part of the democratic process that might get him there.
"In America, everyone has a chance to do all these things," Lomong said. "You follow the rules, people will choose, and if I'm blessed to get that opportunity, I'll get it."
In 2004, Dawn Staley did the flagbearer's honors. In 2000, they went to kayaker Cliff Meidl, who survived a 30,000-volt jolt of electricity in a construction accident and became an Olympian.
Lomong's story is every bit as inspiring.
He knew nothing of the Olympics in 2000, when his friends at the refugee camp in Kenya talked him into running five miles and paying five shillings to watch Michael Johnson on a black-and-white TV set with a fuzzy screen.
At that point, Lomong knew he wanted to be an Olympic runner. He earned his spot at Olympic trials on July 6, exactly one year after he gained his U.S. citizenship.
All three Americans in the 1,500 are naturalized citizens -- Lomong, Bernard Lagat (Kenya) and Leo Manzano (Mexico).
"I feel great," Lomong said Wednesday night. "I feel happy, honored. I'm feeling so blessed to get an opportunity to present the United States of America, to present the United States flag in front of my team."