Park clocked in 3:41.86 to top the podium, China's Zhang Lin got the silver in 3:42.44 and American Larsen Jensen finished third in 3:42.78.

Park wore a headphone before starting his race and seemed to be totally focused on what he was about to achieve. The 19-year-old swam close to Australia's Grant Hackett in the first two laps and began taking over Hackett at 150 meters. He maintained the lead and coasted to win his first Olympic gold.

"This (the gold) was what I'm going after. I lagged behind in the first two laps, but I knew my pace and that I was going to catch up," he said.

"Although the weather was not good today, it was a truly nice day for me," he said.

Dubbed as nation's little brother, Park is the event's world champion and a hugely popular athlete in his country. He is also entered in 200 and 1,500 meters freestyle races.

Australia's Hackett slipped to the sixth at 3:43.84.