Alcaraz, already confirmed year-end world number one, breezed past Felix Auger-Aliassime 6-2, 6-4 in Turin to set up the title match all tennis fans wanted to see after a series of thrilling battles between the pair this year.
The Spaniard has had the better of his clashes with Sinner 10-5, and has won four of this season's five meetings, which have all come in the final of top-level tournaments.
Alcaraz triumphed in the finals of the US Open and Roland Garros, the latter after roaring back from two sets down and saving three match points.
However, Sinner, a 7-5, 6-2 winner over Alex de Minaur earlier on Saturday, became the first Italian to win Wimbledon by overcoming Alcaraz, and the pair have shared the four Grand Slams this season.
"It's going to be pretty difficult. The level we could play is really, really high. Every time we face each other, I think we raise our level to the top," said Alcaraz on court.
Sunday's final has extra spice due to Alcaraz pipping Sinner to the top spot in the men's rankings at the end of 2025 and him contesting his 11th final of the season in front of a partisan Italian crowd.
"Well, I expect at least three or four people in the crowd cheering for me," joked Alcaraz.
"Obviously, the people are going to be cheering for him, but I will try to be really, really focused on my game and on the things that I have to do."
Canada's Auger-Aliassime is an indoor specialist, having won seven of his eight titles on indoor courts, but even he could not handle Alcaraz, who took control of the match by breaking serve in game four of the first set with a brilliant hooked volley.
Alcaraz breezed into a one-set lead with another break of serve and then completed his victory without much difficulty and without having to play his most spectacular tennis.