Portrush - 'If home crowds can't help you, nothing can', says McIlroy
Rahm also won the 2017 Irish Open at Portstewart, which is just 6.4 km down the Causeway Coast from Portrush.
He is yet to win a major, but posted his best result at one of the big four events when finishing tied-third at last month's US Open.
"Ever since the first time I played here, well, in Portstewart two years ago, the Irish crowd is treating me very, very specially," said Rahm, who is from Barrika in the Basque Country.
"I've had great support. And it's the closest I'll ever feel to playing at home, without being at home, really. That's what I think makes it so special.
"When I'm walking around my hometown in Spain, for the most part of the year we get similar weather.
"We're right on the coast, fishing villages. It's just a very similar feel to what I had growing up."
Rahm starts his first round on Thursday at 16:21 SA time, playing alongside Americans Patrick Cantlay and Matt Kuchar.