The Love Island star looked unrecognisable as she dressed up as a glittering mermaid.
Covering her trademark blonde hair with a long brown wig, Olivia went all out with her costume.
Her incredible outfit consisted of a tight leather skirt and matching bra, with long gloves.
She finished her look with a huge headpiece, elaborate sea green make up and endless sparkles.
“I’m sorry but Halloween is life let me live like this or I just won’t,” she wrote on Instagram. “DARK MERMAID WITH MY GIRL @annalingis @thegypsyshrine jewels @houseofharlot outfit @carlbembridgehair hair.”
Liv’s fiancé Alex Bowen also made sure he looked the part for the event, and stuck with the sea theme.
Kady McDermott delights fans with her Halloween make up tutorial on Instagram where she appears to have lost an eye [Instagram/ Kady McDermott]
He dressed as a bloodied pirate, complete with amazing skull make-up down one half of his face.
Olivia was recently forced to defend herself from Twitter trolls who told her to “lay off the burgers”.
Sharing a snap of herself with pregnant BFF Cara De La Hoyde, one follower commented on her Instagram picture saying: “Hahahahah wtf!!!! Cara is glowing and Olivia looks like she needs to lay off the burgers she looks like a fat Chinese kid.”
But the feisty 23 year old responded: “The issue is that something as simple as me not wearing mascara, eye shadow, lashes, eyeliner etc – is causing people to believe I look ‘worse’ or ‘ill’.
“It’s looked at as if it’s controversial to not have hair stuck to my eyes with glitter and black lines on my eyelids.
“Wake up world. I love my beauty produces and my cosmetics but I don’t rely on them to paint a smile on my face. Nor should you.”
“I love those photos from that night,” she continued. “You wanna know why? Cus I felt amazing. I felt confident in my skin with my gorgeous friends and my bridesmaid who is going to be a mother very soon (sic).
“I was happy. I look happy. It feels incredible to finally look at a photo of myself and see real life happiness. Have a word with yourself if you see everything but. Real talk.”