Aguilera, Mraz, Dave Matthews and The Band Perry lead an all-star line-up of artists who will contribute festive tracks to the charity LPs.
Train, Rascal Flatts, Michael Buble, Vince Gill and Amy Grant will also feature on the latest A Very Special Christmas sets.
All proceeds generated will benefit the Special Olympics. More details are expected to be announced at a press conference later today (August 6).
The A Very Special Christmas series was launched in 1987 with a compilation of tracks by Bruce Springsteen, The Pretenders, U2, Sting and Madonna.
Miley Cyrus, Carrie Underwood and Sean Kingston featured on the most recent release A Very Special Christmas 7 in 2009.
Listen to Madonna's 'Santa Baby' below: