Bought by MV Magnier for €2.85 million at the Goffs Orby Sale last year he was the highest priced yearling at that sale and is the first winner for dual Classic winner Finsceal Beo.
Prepared by Aidan O'Brien and ridden by his son Joseph, O' Man River was sent out favourite in a big field of 18 for the mile maiden and won by three-quarters of a length.
Before Sunday's race Ol' Man River had been quoted at 25-1 for next year's Investec Derby, and following his sparkling debut he was trimmed into 16-1 by Betfred for the Classic, while Coral went 20-1.
Ol' Man River is entered for all the big juvenile prizes still to come this year including the National Stakes, Dewhurst Stakes and Racing Post Trophy.
Australian breeders have a chance to breed to Montjeu's Epsom Derby winning son Camelot (IRE), this spring.
A Group I winner at two, before taking the Two Thousand Guineas, Epsom and Irish Derbies at three, Camelot stands at Coolmore a fee of $22,000.
He paraded in great order at the Coolmore stallion parades last weekend as you can see in this picture.