Celebs Flock To Social Media To Show Their Best Halloween Costumes

Halloween is huge in Hollywood ... and celebs from all corners of the industry are showing off their costumes on social media ... setting the bar super high.

Mariah Carey's slaying as Jessica Rabbit ... Kylie and Kendall Jenner are getting creative as Sugar and Spice ... and Barbie Ferreira's getting in the spirit as a ghoul nurse.

Ariana Grande turned back the clock to 1995, dressing up as Elizabeth Berkley's character in "Showgirls" ... with an assist from her friend, Elizabeth Gillies.

Elvira Mistress of the Dark is always a popular -- and sexy Halloween pick -- and this year we've got Lexy Panterra tipping her cap to the cult horror film.

The Kardashians always go all out for All Hallows Eve ... and this year Kim and North West dressed up as Alicia Silverstone and Stacey Dash in "Clueless" ... which came out way before North was born. As if!!!

Over the weekend, stars hit up parties as Paris Hilton did her best Katy Perry impression and Demi Lovato went all Disney princess, and Kate Beckinsale revived Barbarella.