It's the beginning of a brand-new decade, and stars celebrated the start of 2020 in style on Tuesday night, rocking everything from sequins to swimsuits to casual sweats.

Instagram

Zooey Deschanel matched her party's festive decor in a metallic frock by Rachel Antonoff.

Instagram

Bella Hadid showed some skin in a denim Dior bikini and Chrome Hearts bling.

Instagram

Ellie Goulding looked festive in her green lamé crystal-embellished Area mini and sparkly Gianvito Rossi sandals.

Instagram

Justin Bieber and Hailey Baldwin cuddled in coordinating silky shirts.

Instagram

Ahead of her "New Year's Rockin' Eve" performance, Kelsea Ballerini gave fans a glimpse at her appropriately disco-inspired outfit for the evening: a mirrored crop top and matching jeans by David Koma.

Instagram

Alessandra Ambrosio partied it up in a white bralette top and matching maxi skirt with a sultry thigh-high slit.

Instagram

While vacationing in Cabo San Lucas, Mexico, Eva Longoria soaked up some sun with her son Santiago while wearing a white one-piece swimsuit.

Instagram

Over in Miami, Dua Lipa lounged in a leopard-print bikini.

Instagram

Drew Barrymore went casual in a graphic sweatshirt and on-theme glasses to match.

Instagram

Vanessa Hudgens played the princess for a New Year's Eve costume party.

Instagram

Mindy Kaling sparkled from head to toe in her sequined leopard-print dress and glittery glasses.

Instagram

Never one to underdress for the occasion, Mariah Carey got all dolled up in a shimmering gown and "Happy New Year" tiara to spend the night with her twins, Moroccan and Monroe.

Instagram

And Jennifer Lopez and Alex Rodriguez celebrated the start of a new decade at a formal fête, with J.Lo wearing what appeared to be a sexy black catsuit.

Instagram