After saving two match points in his exhilarating come-from-behind victory over Taylor Fritz on Friday, second seed Alcaraz needed no such heroics in a controlled straight-sets win against Norway's Ruud in his last-four clash.
The seven-time Grand Slam champion methodically ground down Ruud from the back of the court in the first set, getting the sole break of serve he needed in the seventh game.
Alcaraz then forced three break points on Ruud's serve, converting the second when the 27-year-old netted an approach shot, to give himself the chance to serve for the match.
The 23-year-old did just that, sealing match point at the second time of asking with an ace as he earned his first final appearance in Paris.
It will be the first meeting between the Alcaraz and Shelton since the American ended Alcaraz's US Open title defence in the quarter-finals earlier this season.
The Flushing Meadows runner-up earned his place in Sunday's final by cutting short the fairytale run of French world number 47 Luca Van Assche 5-7, 6-3, 6-4 in the first semi-final match-up.
"Obviously, Carlos speaks for himself winning the title last week (in Vienna), he's playing great indoor tennis and entertaining tennis as well," third seed Shelton had said of the possibility of meeting Alcaraz.