It was an emotional win for the 26 year old who had struggled with hand injury prior to surgery earlier in the year and being forced to sit on the sidelines for nearly four months.
The Dane came second at this event in 2012 but went one better on Sunday, posting a one under par 71 over the Old Course at St Andrews to finish the week on 18 under par, two shots clear of the American duo of Brooks Koepka and Chris Stroud.
Englishman Chris Wood closed with a bogey-free 65 to finish a shot further back alongside Benjamin Hebert, Bernd Wiesberger, Joakim Lagergren and Kiradech Aphibarnrat.
Olesen began his final round with a three-shot lead over the chasing pack, but followed a birdie from eight feet on the first with a double bogey on the second and a bogey at the next to surrender the outright lead.
He bounced back in style, however, picking up shots at the fourth and fifth holes to return to the top of the leaderboard. After safely parring the next nine holes, Olesen extended his advantage to two strokes with a brilliant birdie from 50 feet at the 15th.
He then parred the notorious 17th to set up a victory stroll down the 18th – one of golf’s most iconic holes – before collecting a cheque for €708,171 which moves him up 99 places up The Race to Dubai (from 124th to 25th), into the top 75 in the World Ranking and to the head of the European Ryder Cup Points List.
“It feels unbelievable. It's been a very tough year and standing here with this trophy is unbelievable. To win over these three golf courses and finishing off especially on St. Andrews is a great feeling.
“Winning after the year I have makes this more personal, and like I said before, very emotional, walking down the 18th at the Old Course to win a tournament. It's been a very tough season for me, and I would like to give a special thanks to my coach's family and friends, and anyone who has been there. I kept believing. I shot a lot of good rounds actually but I couldn't manage to keep it together. It was nice this week just to play three great rounds of golf the first three and kept it together in this last round.”
The leading Australian was Victorian Nathan Holman who finished 19th while Nick Cullen was the only other to make the cut and finished 59th.
Want video tips delivered straight to your inbox? Subscribe to iseekgolf.com newsletters.