Hoyer-Larsen, this year's European and all-England champion, won in straight games as the Olympic final brought together the world's top two players.
Hoyer-Larsen, 30, took the first game 15-12 in 17 minutes and then raced to a 5-0 lead in the second. Dong then staged a fight-back, recovering from 12-7 down to reach 12-10 but his concentration appeared to be broken when, with the Dane serving, he was foot-faulted. The Dane then won his next three service points to take the game 15-10 and the title.
"I did exactly the same thing I had been doing during the whole game. I don't think the call was correct," Dong said.
Hoyer-Larsen, supported during the game by fans who sang Danish football chants, appeared at the post-match press conference with gold written across his forehead.