Harry Styles finally turned 21 on Feb. 1 and threw a huge party over the weekend with a star-studded guest list even including exes Kendall Jenner and Cara Delevingne, as well as current girlfriend Nadine Leopold.

The One Direction heartthrob certainly had an unforgettable night at Lulu's Café in Beverly Hills, accompanied by bandmate Liam Payne and his girlfriend Sophia Smith, along with fellow Brits David Beckham, Chris Martin, Rita Ora, Alexa Chung, Kelly Osbourne, James Corden, Sam Ronson and Remi Nicole.

A photo posted by Kelly Osbourne (@kellyosbourne) on Feb 1, 2015 at 12:33pm PST

Another English celebrity Adele discreetly made an appearance at the bash, amid rumors claiming that her highly anticipated third studio album might feature collaboration with Styles. Us Weekly recently reported that the pop duo was dining together with the "Rolling in the Deep" hitmaker's longtime partner Simon Konecki, manager Jonathan Dickens and director Ben Winston at Craig's in West Hollywood on Jan. 20.

Spotting Jennifer Lawrence sitting with a group of friends, Adele apparently went up to her booth to say hello and chat briefly.

"They exchanged a bunch of laughs for quite awhile before Adele rejoined her table," a source revealed.

Following their recent encounter, "The Hunger Games" actress also celebrated the "Steal My Girl" crooner's birthday, joined by Adam Levine, Rashida Jones, Courteney Cox and Gigi Hadid.

It seems like Styles became friends with his former flames, as Delevingne, Kendall and Kylie Jenner were present at the venue; but most importantly, Leopold was apparently the one who made his night special.

A photo posted by Gigi Hadid (@gigihadid) on Feb 1, 2015 at 10:45pm PST


"Everyone's teasing him, saying he's in love, and he's not denying it. It's the real deal," a source revealed to The Sun (via Mirror). "He's never felt this way about anyone before.

"Harry has spent virtually all his free time in Los Angeles with Nadine. They're infatuated with each other and can't stand being apart," the source added. "There's nobody else he'd rather be with on his birthday."