The Finn, who started the final round with a one stroke advantage, posted a closing round of 70 for a 13 under par winning total of 271, finishing one shot clear of Italian Edoardo Molinari, who claimed second place after a round of 67.
Ilonen birdied the second and fourth holes before a run of 13 consecutive pars meant he took a two stroke cushion to the 72nd hole, and although he dropped his only shot of the day on the last, it was good enough to secure his fourth European Tour title.
Ilonen was inspired by Martin Kaymer's victory last week at Pinehurst and the huge crowd.
"Wire to wire, it was very much a Martin Kaymer inspired win, said the champion. "I sent a message to him last week that I really enjoyed watching golf. I very rarely enjoy watching golf "“ I would rather play golf "“ but Martin's win definitely inspired me.
"I've won four times on The European Tour now, but this would have to be the biggest win of my career. When I looked back from the 18th green, I couldn't believe how many people there were. It was great to see. It was a very humbling moment."
Sweden's Kristoffer Broberg (69) and English pair Matthew Baldwin (69) and Danny Willett (71) shared third place on 11 under par, with Baldwin and Willett joining Molinari as the three players to secure a place in the field for The Open Championship by virtue of their higher world ranking.
The challenge of home favourite Graeme McDowell, who began the final round just two shots back, never really ignited, with the 2010 US Open Champion closing with a round of 71 to finish three shots back, in a share of sixth place with Swede Magnus A Carlsson.
The leading Australian and only one to make the cut was Wade Ormsby who closed with a round of 67 to finish 49th.