Leg kicks, well-timed punches to the head and body, and superior cardio were all the big factors in the 43-year-old prevailing and ending Lewis' six-fight winning streak.
In his post-fight interview with Octagon-side commentator Brian Stann, the heavyweight contender mentioned a lingering back injury, and said this bout with Hunt might have been his last in the cage.
Fight of the Night went to the main event fighters, Hunt and Lewis. What are Derrick Lewis' biggest weaknesses?
Hunt continued the body shot and leg kick attack in round 4.
I predict a knockout win for Mark Hunt late in the fight.
Nguyen had a daring message for Dana White after the fight, taking a swipe at the UFC president after he admitted the promotion had considered dropping the flyweight division. His last win came in March of 2016 and his last fight was in March of this year, when he suffered a third-round KO loss to Alistair Overeem.
Even at 43, Hunt remains one of the most unsafe finishers in the UFC. I've had a lot of fun, traveled the world. Hunt's experience, patience and technical striking ability took over from there.
"This is a pretty good feeling", Hunt said.
UFC Fight Night: Lewis vs. Hunt featured 11 bouts.
But that could not take away from what was a dream day for the New Zealand MMA community, with Dan Hooker producing a stunning second-round knockout over Ross Pearson, while Luke Jumeau claimed a unanimous decision over Dominique Steele in his UFC debut.
After losing the opening round, the 29-year-old Kiwi came from behind to win 29-28 on all three judges scorecards.
In the co-main event Derek Brunson made quick work of Dan Kelly, picking up a first round, KO win.
Hooker, of Auckland, threw the knee as Pearson (19-14) bullied forward with a left hook. Hooker's knee met Pearson's ducking jaw, sending the Brit crashing to the canvas, relieved of his senses.