Laser-focused, the world number two from the U.S. subdued the French wild card and the home crowd to speed through the contest on Court Philippe Chatrier and reach the Roland Garros final for the second time after she lost to Iga Swiatek in 2022.
Ranked 361st in the world, Boisson had downed world number three Jessica Pegula and Russia's Mirra Andreeva in the previous rounds, but she looked deflated against Gauff.
The 22-year-old will, however, pocket a career-changing 690,000 euros in prize money, while Gauff will have the chance to secure her second Grand Slam title after winning the 2023 US Open.
Playing a local favourite at Roland Garros in front of a notoriously fierce crowd can be a challenge even for the most seasoned players, but Gauff came prepared.
"This is my first time playing a French player here. I was mentally prepared that it was to be 99% for her so I was trying to block it out," said Gauff.
Addressing the crowd, she added: "When you were saying her name, I was saying my name to myself just to psyche myself."
Gauff, who can become the first American since Serena Williams in 2015 to lift the Suzanne Lenglen Cup, clearly shifted up a gear after beating compatriot Madison Keys in an error-strewn quarter-final on Wednesday.
Her forehand was solid again, her backhand mesmerising at times, and she served consistently throughout.
Boisson, on the other hand, made an unusual number of unforced errors as her opponent repeatedly forced her to go for the extra shot.
Gauff raced to a 4-0 lead under the Court Philippe Chatrier roof and never looked back, breaking to love at 3-2 in the second set right after Boisson broke her serve for the first time.
The American was on an eight-point winning streak and at the change of ends at 5-2, Boisson placed her towel over her head and hit herself in frustration.
"It's always the plan to start strong," said Gauff. "I knew it was important today. She's an incredible player, she proved to be one of the best players in the world, especially on clay. I'm sure we'll have more battles in the future."
The first Frenchwoman to reach the last four at Roland Garros since Marion Bartoli in 2011, Boisson bowed out when she sent yet another forehand long.