Latrobe ran out a famous winner of the Dubai Duty Free Irish Derby at the Curragh for brothers Joseph and Donnacha O'Brien.
Trained by Joseph and ridden by Donnacha - who are sons of Aidan O'Brien - the 14-1 chance was never far from the pace set by O'Brien senior's Rostropovich.
The latter looked like being swamped at the two-furlong pole, as Latrobe and then Saxon Warrior loomed large, but he refused to buckle and in the end it was only by a narrow margin that Latrobe forced his head in front.
Saxon Warrior, winner of the 2000 Guineas and fourth in the Epsom Derby, had to settle for third as the even-money favourite.
It was a third Classic success of the season for Donnacha O'Brien, who rode Saxon Warrior for his father in the Guineas at Newmarket and also won the Oaks at Epsom on Forever Together.
The victory gave Joseph O'Brien his first as a trainer in a race he won twice as a jockey, aboard Camelot (2012) and Australia (2014).
Appropriately, Latrobe is a son of Camelot and was also winning in the Lloyd Williams colours that Joseph O'Brien sent out to victory in the Melbourne Cup through Rewilding.
Donnacha O'Brien said: "It's pretty incredible and it's not really sinking in yet. It's a special moment."
Aidan O'Brien said of Saxon Warrior: "We'll probably give him a little rest and obviously the Juddmonte (International, at York) and the Irish Champion are the races we've been looking at with him."