Christmas is still months away, but looks like Mariah Carey and Justin Bieber fans are getting a gift a bit early!

Mimi and Biebs are joining forces for a revamped version of Ms. Carey's classic holiday hit "All I Want For Christmas." The track will be featured on Justin's upcoming Christmas album Under The Mistletoe.

The mama of twins Monroe and Moroccan has been hard at work, not only at the studio, but in the gym ... and looks like Mimi's bod is back on track. You go, girl!