The Dane had entered day four a shot behind Wilco Nienaber and with the duo clear of the rest of the field, a two horse race soon developed at Randpark Golf Club.
The local favourite turned in 32 to open up a three shot lead heading into the back nine but Hansen displayed nerves of steel as he birdied the tenth, 12th and 14th to fight his way back to the top of the leaderboard at 19 under.
Nienaber got a remarkable break as his ball stayed dry on the par three 17th but he could not take advantage, and Hansen parred his way home to win by two shots and become a European Tour champion in his 146th appearance.
There were tears in Hansen's eyes after he holed the winning putt to complete a long journey to European Tour victory ten years after turning professional.
He graduated from the European Challenge Tour in 2012 and 2015 but had a breakout year in 2018, claiming two Challenge Tour victories en route to becoming the first Dane to top the Rankings since Thomas Bjørn 23 years earlier.
The 30-year-old had his best year to date on the Race to Dubai in 2019 as he finished in the top 50 on the Rankings presented by Rolex and, after securing an impressive top ten in the Rolex Series at the BMW PGA Championship last month, he is now a winner, making it a Danish hat-trick in 2020 after Rasmus Højgaard's brace of victories.
"It's quite emotional," he said. "This is what we work for, you know? The family watching back home.
"Wilco got in front quite quick, by three shots, and we managed to stick to our game and our plan.
"He's long, he's got some good things with the game hitting it very far and very straight so we knew we had to go out and do our own and do the things we've done the first three days. We succeeded pretty well today.
"I putted really well, almost haven't missed a putt inside six feet and holed a lot of long ones as well."
A two putt birdie on the par five fourth moved Nienaber two ahead and he holed a 20 footer for a birdie on the next but Hansen followed him in from five feet after a wonderful tee shot on the par three.
An approach to 12 feet on the sixth handed Nienaber a three shot lead that he held at the turn but Hansen cut the gap from 12 feet on the tenth.
The leading duo both did well to save par on the 11th and Hansen played an excellent pitch over a bunker on the par five 12th to set up a birdie and cut the gap to one.
Nienaber leads the European Tour in distance off the tee at an average of 337 yards but he failed to take advantage of the par five 12th and 14th and, when Hansen made it a brace of birdies on those holes from five feet at the latter, we were tied at the top.
The 20-year-old looked in big trouble when he found the wrong tier off the tee at the par three 14th but produced possibly the two putt of the season, going up the slope and through the fringe on a left to righter to get within ten feet and stay at 19 under.
He was inches from the water on the 17th and could not get up and down from an awkward stance, as Hansen played the par three beautifully to make a par under pressure.
Hansen went from rough to sand up the 18th but played an excellent bunker shot to eight feet, completing a bogey free round as Nienaber carded a bogey after finding a bunker off the tee to sign for 70.
Norris made a single bogey and six birdies in his round, while Surry signed for a 67, one better than Cockerill and two lower than Stone.