The home hero recorded a closing 65 to get to 22 under and beat Willett by one shot, so becoming the first Italian to win his national Open twice since the event became part of the European Tour in 1972.
The 2006 champion also became the first Italian to win any European Tour event twice, as he claimed his fourth win and his first since the 2012 Open de España.
The victory came in his first event since the Barclay’s in New Jersey three weeks ago where he missed the cut in the opening event of the FedEx Cup Playoffs.
Followed by an enormous gallery, Molinari turned in 31 and held a four-shot lead with six holes to play; but Masters Tournament winner Willett is nothing if not resilient, following up a birdie on the 13th hole with an eagle on the next to cut the gap to one shot.
There were nervy moments from both players in the closing stretch, and Molinari was forced to produce a miraculous recovery shot from the trees after pushing his drive right from the 18th tee.
When Willett holed for par from 12 feet on the 18th green to sign for a round of 66, Molinari needed to follow him in from three feet and duly did so to become the second home player to win his national Open in as many weeks, following Joost Luiten’s victory at the KLM Open.
“It’s been a rollercoaster. It’s amazing to see this amount of people out here supporting me.“ said the winner,
"I had the ideal start, I couldn’t have started any better. When I birdied the 12th I went four shots clear, and thought maybe I could relax a bit but then I got punished straight away. Coming in I had nothing left, I was just playing with my soul.“I was hitting some horrible shots, but somehow I managed to bring it in.
"It feels incredible, this win was so much harder than my first one in 2006. Back then there were no expectations, but this time was different. A lot of people thought I would win, and I didn’t want to let the fans down.”
Spaniard Nacho Elvira and England’s Chris Paisley both secured their European Tour cards after finishing in a tie for third place on 18 under par, courtesy of respective rounds of 65 and 68.
The English duo of David Horsey (65) and Richard Bland (69) rounded out the top five after finishing on 16 under par.
Richard Green headed the Australians when he finished in 16th position.
The European Tour now moves to Germany for the Porsche European Open ahead of the Ryde Cup in eleven days.
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