Kim completes South Korean archery sweep with individual men's gold
South Korea cemented their status as archery supremos with their fifth Paris gold medal, adding to the women's individual title and the three team golds - in men's, women's and mixed.
Ellison had to settle for the silver in the individual men's event and South Korea's Lee Woo-seok won the bronze.
Kim and Ellison took turns winning the first four sets. With the fifth set at 4-4, the crowd were on the edge of their seats as the pair got perfect scores to force a shoot-off.
Both men fired their arrows into the middle of the target but Kim's was closer to the centre and won the gold.
The two archers, who have a long history of competing against each other, expressed their deep mutual respect.
"If (Lionel) Messi and (Cristiano) Ronaldo are the best in football, then maybe we are the duo in archery," Kim said.
The Korean archer had also knocked out defending champion Mete Gazoz 6-4 in the quarter-finals and the Turk looked devastated as his coach tried to console him.
Losing gold did not upset Ellison, a five-times Olympian, who said he valued the skills gained by competing against the world's best, calling the process "steel sharpening steel."
"When I go to a tournament, I know who I'm going to be shooting against," he said. "Those are the guys I compare myself to."
But Ellison and Kim acknowledged that Paris may not be the last time they meet.
"I think we're going to do a rematch in LA," Ellison said, referencing the 2028 Games.