Chung also became the first Korean in history to reach the quarter-finals of a Grand Slam tournament, reports Efe.
"When I was young I just tried to copy Novak because he was my idol," Chung said after the win.
This was only the fifth time Djokovic failed to reach at least the quarter-finals in Melbourne, in his 14th appearance in the first Grand Slam event of the season.
It seemed as though the elbow injury that forced Djokovic to end his 2017 season in July returned to bother him again against Chung, who had won an upset victory against Germany's Alexander Zverev, a top 10 player, in the previous round 5-7, 7-6 (7-3), 2-6, 6-3, 6-0.
Chung started the match strong, building a 4-0 lead in the first set, but Djokovic rallied back, pushing the set into a tie break, which his rival clinched.
Djokovic called for the physiotherapist to massage his elbow at the end of the first set of his 950th professional match.
Again in the second set, Chung squandered a 3-0 lead, but managed to break Djokovic's serve one more time to seal the set.
The 21-year-old Chung had an early break in the third set, with Djokovic trying to fight back only to lose the tie break.
After three hours and 21 minutes of contest, Chung earned his first win over Djokovic in two career matches, after the Korean player lost at the same stage in Melbourne in 2016.
For a place in the semi-finals, Chung will take on the United States' Tennys Sandgren, who will also be making his debut in a Grand Slam quarter-final.
Sandgren beat fifth-seed Dominic Thiem of Austria 6-2, 4-6, 7-6 (7-4), 6-7 (7-9), 6-3, after previously upsetting former champion Stanislas Wawrinka of Switzerland in the round of 64.
(This story has not been edited by Social News XYZ staff and is auto-generated from a syndicated feed.)
