Billie Eilish was a real-life Holiday Barbie at the 2021 Met Gala.

As her debut on the infamous Metropolitan Museum of Art steps, the singer, who served as co-chair for Monday’s event, stepped out in the ultimate old Hollywood glam look.

This year’s theme was In America: A Lexicon Of Fashion.

RELATED: Billie Eilish Gets Candid About Her Complicated Relationship With Social Media

Inspired by the Holiday Barbie, the Oscar de la Renta gown also gave us major Marilyn Monroe vibes.

Billie Eilish Photo: Getty Images
Billie Eilish Photo: Getty Images

According to Eilish, who chatted with Keke Palmer for Vogue, she wanted to feel like the “belle of the ball.”

RELATED: Billie Eilish Says She Wishes Men ‘Cared More’ About Texas Abortion Bill: ‘I’m So F**king Tired’

Adding that the Holiday Barbie was “my favourite thing in the world, I would ask for it every year.”

Eilish served as co-chair alongside Timothee Chalamet, poet Amanda Gorman and tennis pro Naomi Osaka.

The musician later revealed how she’d agreed to wear the Met Gala dress if designer Oscar de la Renta were to go fur-free.

She wrote, alongside some stunning snaps: “Thank you Oscar de la Renta for designing this BEAUTIFUL dress and bringing my ideas and vision to life.

“It was an honour to wear this dress knowing that going forward oscar de la renta will be completely fur-free!!!!”

“I am beyond thrilled that @fernandogarciam1205 and @tokibunbun and the entire team heard me on this issue, and have now made a change that makes an impact for the greater good, not only for animals but also for our planet and environment too,” she went on.

“I’m honoured to have been a catalyst and to have been heard on this matter. I urge all designers to do the same.”