"Today, for 15 holes, I played the best golf I can ever play on the course with the weather we had", Rahm said.
Im, who was tied for the lead with Benjamin Hebert after the first two rounds, birdied five of his opening 14 holes and scrambled superbly at the end to shoot a 68 and stay alongside Rahm.
Beginning the day tied for the lead alongside Im, Rahm holed out from 150 yards to eagle the par-five fourth and move two ahead.
Rahm shot a second straight 5-under 67 in the third round.
However, by that time Rahm had already done more than enough to get his hands on the title in only his second start in Europe since joining the European Tour which will also place him back into the top ten in the world rankings.
"I know that Government support is required and I have been working to secure that support". My putting and short game has never been my best ally on links courses, but this week has been the opposite.
Daniel Im battled hard to stay tied at the top at Portstewart heading into the final day
Spanish star Jon Rahm says it is "really special" to join his compatriots Seve Ballesteros, Jose-Maria Olazabal and Sergio Garcia in becoming an Irish Open victor. "But if you had told me I was going to shoot 24 under in this weather, and win by six, I would have probably said, 'You're insane".
Ruddy himself said afterwards "it's the people that make it so special" and 2018 will showcase to the world not just one of his masterpieces but the famous Donegal hospitality. Also playing are Jon Rahm, Justin Rose, Tommy Fleetwood and Thomas Pieters.
Julien Quesne and Scott Hend both shot 64s for the lowest round of the day and are fifth and sixth, respectively.
Sadly, for him, his record lasted only an hour as Scotland's David Drysdale reached -17 with an inspired 63 - rounded off with seven consecutive birdies.
Four strokes back is Love, who at 53 years and two months is seeking to supplant Sam Snead (52 years, 10 months) as the oldest player to win on the Tour.
Lilian Calmejane grits teeth to win Stage 8 of Tour de France
Team Sky race leader Chris Froome said: "Today some teams wanted the [race leader's] yellow jersey... we couldn't let them go". That's the monstrous challenge lurking on Sunday for the 193 already exhausted and sunbaked riders who have made it this far.