The peerless trio of Kim Woo-jin, Ku Bon-chan and Lee Seung-yun roared to a 6-0 win on a baking hot day at the Sambodromo, clinching South Korea's fifth team title and fourth in the last five Olympics.
"I've been waiting for this moment, to get gold, for four years," beaming world champion Kim, who fired a 72-arrow world record during Friday's ranking round, told reporters.
"We trusted each other, and it happened. It just happened."
The U.S. team, who ended the South Koreans' run of three titles in the London semi-finals, were left with a second successive silver after the Koreans closed out the match in style with a run of perfect scores.
Australia celebrated their first archery medal in 12 years by defeating China for the bronze.
All three Olympic debutants, Kim, Ku and Lee, showed no sign of rookie nerves as they trampled over Netherlands and Australia before saving their best for the gold medal-decider.
Cheered by a rowdy Korean contingent in the terraces, the trio threw down the gauntlet in the opening set, hitting the innermost gold circle six times in succession to score the maximum 60 points.
More than a statement, the opening salvo was a winding blow for the more seasoned U.S. team of three-time Olympian Brady Ellison, Jake Kaminski and Zach Garrett.
They shot well in response but could manage only 57 points for the set and from there the pattern of the match was fixed.
The Korean onslaught was relentless.
The 23-year-old Ku took the perfect score of 10 points with all six of his arrows, and missed only once.
Standing on the podium in the middle of a team of world champions, Ku kissed his medal and beamed, while Lee wiped a tear from his cheek during their national anthem.
The team sealed South Korea's 20th archery gold medal from 37 Olympic titles contested since the sport returned in its modern format in 1972.
With its professional teams and punishing training regimes, the depth of Korean archery is unmatched and the nation will be disappointed if it fails to sweep all four titles at Rio.
"There really wasn't anything we could have controlled," Kaminski, who lost the London final against Italy with Ellison, said resignedly. "I definitely feel we left it all out there."
(Reporting by Ian Ransom; Editing by Ed Osmond and Bill Rigby)
