While they've been seen in public together, Katy Perry and John Mayer have avoiding making any kind of public comment on their romance...until now.

Late on Christmas Day, Katy tweeted a picture of her beau in a full Santa Claus outfit, minus the beard but with a come-hither look on his face.  Her caption? "Santa Baby."

As previously reported, the couple spent Christmas together with Katy's family.

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