Ariana Grande is celebrating a HUGE milestone tomorrow — she turns 21 years old! So how did the "Problem" singer decide to prepare for her big day? She threw a birthday bash at Walt Disney World with all her friends — not to mention Mickey Mouse, Cinderella, and Prince Charming were all there, too.
Click through the gallery to check out all the cutest photos from Ariana's bday event. Tell us in the comments: How are you celebrating your next birthday? Don't forget to wish Ari an early happy birthday in the comments, too!