car shots Gwyneth Paltrow Chris Martin

Jennifer Aniston had a party and everyone came! And we mean everyone -- including Gwyneth Paltrow! Who knew both of Brad Pitt's exes were pals?!

Jen's bash kicked off around 6pm on Sunday night, and from Gwyneth and her hubby Chris Martin, to the usual suspects (Chelsea Handler, Courteney Cox, Tobey Maguire and his wifey Jennifer Meyer), the party was totally A-list. Gwynnie's Iron Man co-star Robert Downey and his wife Susan were there, along with Jen's Horrible Bosses co-star Jason Bateman.

Jen and fiance Justin Theroux went shopping for a Christmas tree last week, so it looks like the house was fully decked out, and she even got her hair done on Friday night.

A photographer on the scene tells X17online exclusively:
    "It was one of the most star-studded parties I've ever seen. Even people you didn't think knew Jen were showing up. To get Gwyneth Paltrow and Chris Martin to come together was a miracle in itself."