The 22-year-old had been linked with a number of clubs across Europe but opted to remain in Ligue 1.
Monaco finished below Reims in the truncated league campaign but Disasi has no doubt he is taking a step up in joining Niko Kovac's side.
"I'm delighted to be involved with AS Monaco," he told the club's official website.
🖋 🇫🇷 AS Monaco are delighted to announce the signing of Axel Disasi. The French defender has penned a deal with us that runs until June 2025.pic.twitter.com/nrgWWEfvFA— AS Monaco EN (@AS_Monaco_EN) August 7, 2020
"This is a great opportunity for me to demonstrate my qualities at the highest level and to continue my progress at a club with high ambitions.
"I'm looking forward to starting training with my new team-mates and I'm going to put all my energy into helping the team achieve its goals at the end of the season."
🔁 Arrivé au #SDR à l’été 2016, le défenseur central Axel Disasi rejoint l’@AS_Monaco.— Stade de Reims (@StadeDeReims) August 7, 2020
Aligné à 55 reprises (3 buts) en 🔴 et ⚪️, l’athlétique ancien numéro 6️⃣ stadiste vient de parapher avec le club de la Principauté. Bonne continuation Axel ! pic.twitter.com/M8VZAxSR5V