The "We Belong Together" hitmaker celebrated the milestone on Friday (27Mar20) and, taking to Instagram, "Toxic" star Britney penned a sweet tribute to the music icon.
"Happy Birthday @MariahCarey !!!!! You are one of the main reasons I started singing," she gushed, alongside a photo of herself with Mariah at a 2017 party. "Your Butterfly album never gets old even after 20+ years ….. it’s simply a classic and I will be listening to it today as I work out in the gym !!!!! Have a wonderful birthday!!!!!! God bless."
Soon after sharing the post, Mariah responded in the comments, writing back: "Love you Britney!!!! And I'll be listening to Stronger as a morale booster! Thank you for this beautiful message."
Britney was one of many celebrities sending their birthday wishes to Mariah, with John Travolta celebrating her, Lady GaGa, and Quentin Tarantino's birthdays on Friday, and "Stranger Things" Millie Bobby Brown and actress Kerry Washington also sharing messages.
Mariah celebrated her big day by heading into the studio to record new music, writing alongside a snap of her standing by a microphone: "Starting 327 with a new song."