Sinner’s 65-week reign as world number one was ended by Alcaraz when he lost to the Spaniard in September’s US Open final.
But he regained top spot in style by conceding the fewest games on route to the Paris title since the event switched to hard courts in 2007.
The Australian Open and Wimbledon champion dropped only three points across his five service games and was entirely untroubled on his way to capturing the first set.
Sinner won 93% of points on his first serve in the opener and was dominant in the rallies, winning 17 of 25 points from the baseline.
Auger-Aliassime raised his level, saving multiple break points in the second set before edging 4-3 ahead, but Sinner continued to starve his opponent of opportunities.
Despite briefly appearing to struggle physically, Sinner levelled at 5-5 after being taken to deuce for the first time while serving to stay in the set, and both players held out for a tie-break.
Producing just three unforced errors throughout a hard-fought second set, a single mini-break proved enough for Sinner, who took his first championship point to lift the tournament’s unique tree-shaped trophy for the first time.
BBC News