BBC News: Irish Grand National: Rank outsider Freewheelin Dylan wins at odds of 150-1
Ridden by Ricky Doyle, the Dermot McLoughlin-trained horse produced a stunning front-running performance to record the shock success.
The nine-year-old was always travelling well and saw off all his challengers to win by a length and a quarter.
Run Wild Fred (9/1) was second, with Enjoy D'Allen (40/1) third and 9-2 favourite Latest Exhibition fourth.
A field of 28 lined up at the start but Freewheelin Dylan dominated the race, held over three miles and five furlongs.
Doyle's mount, making his first appearance since finishing last of eight runners at Punchestown in October, was in front after jumping the first fence and was never headed.
'It was like a dream'
"I could not believe it.
I thought everything was too good to be true.
His jumping was out of this world," winning jockey Doyle told ITV Sport.
"It was like a dream the whole way, how well he travelled, unbelievable.
"I'm just so happy. This is everything to me."
McLoughlin's father won the Irish national as a jockey in 1962 and his stable is based near Fairyhouse.
"I have been coming here since I was a young boy and I wanted to win this race from a long time out," explained the victorious trainer.
"Coming here I knew he enjoyed the ground and he just kept galloping. Ricky said he would be really positive and he was."
Enjoy D'Allen came in three lengths behind Run Wild Fred, with Latest Exhibition next under the burden of 11st 10lb.