Celebrity BFFs ... Taylor Swift partied like it’s 1989 with Karlie Kloss, Haim, Jay Z, Beyonce, Justin Timberlake and Sam Smith. Picture: Instagram/taylorswift Source: Supplied

The Shake It Off singer marked her 25th birthday with a posse of her famous besties at her New York home.

Beyoncé, Jay Z, Justin Timberlake, Selena Gomez, singer Sam Smith and supermodel Karlie Kloss were all there.

JT seemed to be having ball, sporting a mask in the shape of the “poo” emoji, while even Swift seemed to pinch herself over the guest list.

5 Seconds of Summer’s Michael Clifford turned up with a huge teddy bear gift.

“So this is being 25…. #WHAT #bestbirthdayEVER,” Swift wrote on Instagram about the party.

Other guests included girl group Haim, Charlie XCX, Emma Roberts, Chrissy Teigen, Jaime King, Kelly Osbourne, Nick Jonas and Olivia Culpo.

Girls actor and writer Lena Dunham, gave Swift a charm necklace featuring a picture of Swift’s cat, Olivia Benson, which the singer calling the b’day gift her “new most cherished possession”.

The birthday girl wore a tartan crop top and matching pants and at one point wore a Santa hat at the party, held after Swift performed at the iHeart Jingle Ball at Maddison Square Garden.

Guests at the party dined on pizza, with the Daily Mail saying that around 20 boxes were seen being delivered to Swift’s Tribeca home.