After dropping the first set and trailing in the second, Chung found his groove to win 3-4 (5), 4-3 (2), 4-2, 4-2.
Chung had been the standout player of the tournament winning all of his matches en route to the final, including a dominant 4-0, 4-1, 4-3 (1) display against Rublev in the group stage.
Despite getting his tournament off to a shaky start, No. 1 seed Rublev produced a stunning display to see off Borna Coric in the semifinals, and it was the Russian drew first blood in the final, taking a hard-fought first set in a tie break.
From that point, it looked like Rublev might take control of the encounter as broke the South Korean in the first game of the second set built a 3-1 lead.
However, Chung refused to make things easy, winning back-to-back games to set up another tie break, which he won.
That was the turning point for the South Korean, who won the next two sets to seal the title in an hour and 57 minutes.