Conflated joined stablemate Galvin in the Gold Cup picture with an 18-1 shock win at Leopardstown.
The outsider, available at odds of 50-1 on the eve of the Paddy Power Irish Gold Cup, came home in front of Minella Indo and Janidil.
Jockey Davy Russell made a race winning move entering the straight, sending his mount five lengths clear of the pursuers.
Reigning Cheltenham Gold Cup winner Minella Indo battled on well, but Conflated grew the gap to six-and-a-half lengths at the line.
The winner is as low as 7-1 with the race sponsors for the Festival feature, three points longer than Savills Chase scorer Galvin.
Both horses are trained by Gordon Elliott, who won the race in 2016 with Don Cossack.
"I know he's a horse with a massive engine but he can be very hot or cold and it's great for the whole team that he's won this.," the trainer said.
"We've a massive team behind us and to win a race like this is unbelievable."
Conflated will collect a 150,000 euro bonus from the Saturday sponsors if he adds the Boodles Cheltenham Gold Cup to his CV.
Minella Indo is their 7-2 favourite after he bounced back from his comprehensive King George defeat to take the runner-up spot.
Russell, aboard Galvin when he raced into Cheltenham contention on December 28, was impressed with Conflated's attitude.
"He jumped super and did everything really, really well. He jumped straight as a die, he can hang a bit but nothing today," he said.
"It was either one or the other - I was either gone too soon or they would never catch me. To be fair to the horse, he kept responding. The more I pulled out of him, the more he responded."
Elliott won the race two years ago with Delta Work and the nine-year-old finished sixth on this occasion.
Cheltenham Gold Cup best odds: 7-2 A Plus Tard, 9-2 Galvin, 6-1 Minella Indo, 10-1 Protektorat, Al Boum Photo, 14-1 Tornado Flyer, 20-1 Chantry House, 22-1 Royale Pagaille, 33-1 Champ, 40-1 bar
Results from day 1 of the Dublin Racing Festival
1.05
1 Minella Cocooner 11-1
2 Minella Crooner 100-30
1.35
1 Vauban 9-4
2 Fil Dor 6-5f
3 Il Etait Temps
2.10
1 Blue Lord 5-2
2 Riviere D'etel 2-1f
2.45
1 Good Time Johnny 17-2
2 Rightplacerightime 7-2f
3 The Little Yank 80-1
4 Whatsnotoknow 25-1
3.15
1 Conflated 18-1
2 Minella Indo 11-2
3 Janidil 7-1
3.50
1 A Wave Of The Sea 9-2
2 Grange Walk 15-2
3 Batcio 11-1
4.25
1 Facile Vega 8-11f
2 Sandor Clegane 17-2
