No, it wasn't the Grammys, or any other Hollywood awards ceremony, that brought together some of the biggest names in 2015, it was One Direction's Harry Styles' 21^st birthday. Indeed it was a star studded event last January 31 as Styles had a full-on celebrity-studded guest list including Jennifer Lawrence, Adele, and Kelly Osbourne.

Some of the other names who attended the party were, Chris Martin, who was reportedly Lawrence's date, David Beckham, Cindy Crawford, Courtney Cox, Adam Levine, Zach Braff, Kendall Jenner, Cara Delevingne, Rashida Jones and even Styles' rumored girlfriend and model Nadine Leopold.

It was reportedly a fun-filled birthday bash with several birthday cakes, one shared by Rita Ora who was also at the party, on her Instagram. She captioned the photo with one of Styles' cake saying "One of his cakes @harrystyles #lastnight #birthdayboy #happybirthday," Ora wrote.

There were a lot of photo moments reportedly, as Styles had a "star-studded" photo booth. One of E! Fashion Police co-hosts, Osbourne, posted a photo on her Instagram capturing one of the photos from their pictorial with Styles, Delevigne and Jones, captioning the photo with "Last night was so much fun!!! #HappyBirthday @harrystyles ????," Osbourne wrote.

The night couldn't be more special according to reports if it weren't for Styles' new rumored fling, Leopold. An Insider of US Magazine shared some reportedly sweet moments between the birthday boy and the model saying, "she brought a bunch of her ... girlfriends and mostly let Harry have his space."

Also, it is rumored that although Leopold didn't stay long, she and Styles got together after. "He ended the night with her," the source said. "He would run over to her and her friends and they'd get all excited and really wanted to make sure he was having fun," the source added.

Meanwhile, although one of the most important people in Styles' life wasn't present at the party, his mom, Anne still got to see it. "He FaceTimed his mom during the party," the source said, "He swung his phone around the room so she could see the party."