Rune avenged his loss to Auger-Aliassime in last weekend's final in Basel. He will take on defending champion Novak Djokovic (35) or Stefanos Tsitsipas (24) for the title in the French capital.
"I lost to Felix last week in two sets, beat him this week in two sets. I learned a lot from last week, and trying to do a lot differently today. I'm super happy that it worked," said Rune.
The 19-year-old is through to his fourth successive final. He beat Tsitsipas to lift the trophy in Stockholm last month after finishing as the runner-up in Sofia.
"You're always a bit more nervous when it's the final because it's so close to winning the tournament," said Rune.
"It's going to be super tough... For me it's just really about playing my game because that's what can get me the closest to winning tomorrow."
A quarter-finalist at this year's French Open, Rune collected his fourth straight victory over a top-10 player this week by ending Auger-Aliassime's 16-match winning run.
The Canadian was attempting to become the first man to win four tournaments in as many weeks since Ivan Lendl swept five over a five-week span in 1981.
Auger-Aliassime paid the price for a hesitant swinging volley after a gentle looping return from Rune as he conceded the lone break in the third game of the opening set.
Rune then broke the eighth seed twice in succession to start the second set, inflicting a first defeat on Auger-Aliassime since his first-round loss at the Astana Open a month ago.
Having arrived in Paris with just three match wins at the Masters level, Rune began his run to the final this week by beating three-time Grand Slam champion Stan Wawrinka in the first round.
He then took down Hubert Hurkacz followed by Andrey Rublev before seeing off Carlos Alcaraz as the world number one retired with injury while trailing by a set Friday.
Rune is set to climb to a new career high of 12th after reaching the final. He will break into the top 10 for the first time if he wins the title.
Djokovic is bidding for a record-extending seventh Paris crown and 39th Masters triumph.
He has won the past seven meetings with Tsitsipas, who is making his first semi-final appearance at this event.
The Greek fifth seed has a tour-leading 60 wins this season. He has reached seven finals in 2022 which is joint most alongside Alcaraz.
