The world No 4 became the sixth Spaniard to win the tournament since it achieved European Tour status in 1972, finishing on 20 under overall and two shots clear of Ireland’s Paul Dunne.
And Rahm – who follows the likes of Seve Ballesteros and Sergio Garcia in winning his home event – admitted that he found it difficult to handle the expectations placed on him.
“I’m just happy to play the way I did and to get it done,” Rahm sad after his third European Tour victory.
“It’s probably the hardest Sunday I’ve ever had to play because the amount of crowds I was carrying.
“I saw the willingness and the feeling that everybody had to want me to win.
“They were pushing so hard and I felt that. As a golfer it’s hard to deal with the public’s emotions, so I tried to isolate myself and that’s perhaps why I didn’t play my best golf.”
Overnight leader Dunne led by one shot heading into the final round, but Rahm stamped his mark on proceedings with birdies at the first, second and seventh holes.
The tournament was eventually decided on the short 17th as Rahm escaped with a par after almost sending his tee shot into the water, the ball just holding up in the rough.
Rahm’s closest challenger, Nacho Elvira, was not so fortunate at the 17th when he found the hazard and his hopes of a maiden victory disappeared with a double bogey five. Moments later Rahm birdied the last to secure victory.