Italy's Francesco Molinari came up agonisingly short in his bid for back-to-back wins and a third Italian Open crown as Thorbjorn Olesen held his nerve to claim the fifth European Tour title of his career.
Olesen carded a closing 64 at Gardagolf to finish 22 under par, a shot ahead of home favourite Molinari, who had won the BMW PGA Championship at Wentworth last week.
The two players had been tied for the lead with two holes remaining, but Molinari dropped just his second shot of the week on the 17th and Olesen birdied the same hole in the group behind to take a two-shot lead.
Molinari refused to throw in the towel and holed a curling birdie putt on the last from 40 feet to complete a 65 and pile on the pressure, but Olesen got up and down from a greenside bunker for par to secure the first prize of €1 million in the second Rolex Series event of 2018.
Graeme McDowell also shot a 64 but it was only enough for a share of fifth place after he finished on -17, five shots off Olesen.
Elsewhere Paul Dunne hit a round of 68 to finish on -11 for the tournament.
England's Lee Slattery finished alone in third after a closing 67, despite having to get a replacement caddie after 13 holes after Max Cunningham signalled he could no longer continue due to a pelvic injury.
Spain's Rafa Cabrera Bello was fourth on 18 under with Lee Westwood, Graeme McDowell and Andy Sullivan a shot further back in a tie for fifth.