The former Made In Chelsea star, 25, unveiled the cute new piece of body art in an Instagram snap uploaded on Friday night (17 October).
In the photo, Millie is wearing a gorgeous white floaty dress with purple pattern and cut away panels that reveal what appears to be a new body inking.
If real, the Hamsa symbol - a palm-shaped amulet believed to protect wearers against evil - would have been Millie's fourth tattoo.
She already has a butterfly on her lower back, three stars on her upper left shoulder and another one that she has never disclosed.
Millie still has a way to go before she can catch up with husband Stephen Manderson's - aka rapper Professor Green - extensive tattoo collection, though. He has dozens all over his body!
However, Millie is also known to be fan of fake body bling. She recently admitted that she's a big fan of jewellery-inspired temporary tattoos and told fans she had packed some for her holiday to Dubai.
It may not be real Millie, but we love it!
The next day, Millie channelled her inner Rihanna by wearing a winged tattoo just below her boobs.
Wearing a gorgeous pink bikini with gold clasps, Millie wrote: "Wishing I was riri #rg @cbyclarissa @divineinklondon@beachriot."
We think temporary tattoos are a great way to try out new looks - and keep us all guessing!
Do you prefer temporary tattoos or the real thing? Tell us below and you could win £50!
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