The world number four began the day behind overnight leader Paul Dunne but a birdie-birdie start from the Spaniard saw him tied for the lead after two holes.
Rahm is the sixth Spaniard to win the Spanish Open since it became part of the European Tour in 1972, joining some illustrious company including Seve Ballesteros, Sergio Garcia and Miguel Angel Jimenez.
"It's been wonderful. It's truly been the hardest Sunday I've ever had in any tournament that I've won because the crowd wanted it so much and I wanted it so much".
Jon Rahm has fired a five-under 67 to claim a maiden victory on home soil at the Open de Espana in Madrid. Triumph the previous one join and also I'd to win that collection of winners that are Spanish and to around my newbie and pro livelihood within such a way, it'so tricky to explain how good it feels and it is.
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At the other end, Marco Reus forced a flying save from Ralf Faehrmann as his long range free-kick fizzed towards the top corner. However, both teams staged a well-positioned defense and defused most opportunities in the opening period.
The round of the day went to George Coetzee, who shot a magnificent nine under 63 to rocket up the leaderboard. You can tell how excited everybody is.
Ian Poulter's hopes of lifting a second PGA Tour title in three weeks came crashing down at Hilton Head when the Englishman suffered a calamitous final nine holes. I felt that. And it was hard to deal with. "I came for them mainly, so I'm just glad I can win this one for the Spanish people". Everyone seemed to want me to win.
"I'm a little disappointed, but Spain has a great champion in Jon and I'm sure he'll win many more of these".
Elvira handed the title to Rahm when he hit his tee shot into the water at the 17th and made a double bogey just moments after the champion's tee shot hung up on the bank, allowing him to save what turned out to be a crucial par.
Elsewhere, Japan's Satoshi Kodaira beat Si Woo Kim of Korea at the third extra hole to win the PGA Tour's Heritage Classic at Hilton Head in SC.
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