Aged just 23, the fresh-faced Web.com Tour graduate displayed ice-cool nerves as he stormed home with five consecutive birdies to fire a seven-under-par 63 on the tree-lined layout at Waialae Country Club.
Co-leader overnight with fellow rookie and good friend Scott Langley, Henley mixed eight birdies with a lone bogey to post a record 24-under total of 256 in the US PGA Tour's first full-field event of the season.
When he rolled in an eight-footer to birdie the par-five last, one of several stunning clutch putts he made on the day, he gave a roundhouse sweep with his right arm in celebration.
"I don't really even know what just happened," a smiling Henley told Golf Channel after becoming the event's youngest winner, eclipsing compatriot Ben Crenshaw who was aged 24 when he triumphed in 1996.
"This is the most nervous I have ever been and that's the hardest thing I have ever done. I was just trying to stick to my routine and stay committed and stay in the present. I had to battle Tim (Clark) and I am just kind of speechless right now."
With his spectacular triumph, Henley earned an invitation to the Masters and became the first rookie to win on his debut as a US PGA Tour member since compatriot Garrett Willis at the 2001 Tucson Open.
"It's been my goal to make it to the Masters my whole life," said Henley, who won twice last year on the US PGA Tour's feeder Web.com circuit and shared low amateur honours with Langley when they tied for 16th at the 2010 US Open.
South African Tim Clark, bidding for his second title on the circuit, signed off with birdies on the last four holes for a matching 63 to secure second place.
First-round leader Langley faded with three bogeys on the back nine, carding a 70 to finish in a tie for third at 17 under with fellow American Charles Howell III (66).
Henley began another warm day of light breezes at Waialae tied at the top with playing partner Langley and he benefited from a two-shot swing at the par-four first to move two strokes clear.
While Henley birdied the hole after hitting a superb approach to within three feet, left-hander Langley wound up with a bogey after finding the right rough off the tee and also with his second shot.
Langley missed birdie putts from inside six feet at the second and sixth before duffing a chip from greenside rough to bogey the par-three seventh and slip three strokes off the pace.
Henley dropped his first shot in 51 holes at the par-four eighth, where he pulled his drive into the left rough and ended up in tangly grass behind the green with his approach.
However, he immediately recovered with a two-putt birdie at the par-five ninth to reach the turn two strokes in front of the chasing pack.
Henley rolled in a nine-foot birdie putt at the 10th to maintain his cushion and did well to save par from a similar distance at the par-four 11th after pulling his tee shot on to a cart path.
He delivered a dagger blow by draining a 45-footer to birdie the 14th and stretch his lead to three strokes, then sank 12-footers at the 15th and 16th to keep the charging Clark at bay.
Remarkably Henley birdied the last two holes for good measure to complete a commanding debut win and earn a three-year exemption on the US PGA Tour.
Asked how he had gained the self-belief to secure victory so early on in his US PGA Tour career, Henley replied: "I think last year on the Web.Com Tour.
"I was in this situation a lot in the last five or six tournaments, actually the last 10. I had a good last half of the year and that prepared me."