In addition to her mother, Betty, and husband, Jim Toth, a number of A-list celebs attended Witherspoon's bash, including Jennifer Aniston, Justin Theroux, Courteney Cox, Kate Hudson, Robert Downey Jr., Nicole Kidman, Keith Urban, Tobey Maguire, Jason Bateman and Matthew McConaughey.
Erin Foster -- daughter of GRAMMY-winning producer David Foster -- shared a pic of her and Hudson cuddling up close to the birthday girl alongside a group of fellow blonde beauties.
Taylor Swift was there, too, and she even put on a private show for Witherspoon and the lucky guests! Hudson shared brief videos of the mini concert on Snapchat.
That wasn't the only performance of the night, however. At one point, Urban played the guitar while Witherspoon belted out Lynyrd Skynyrd's "Sweet Home Alabama." As many fans of Witherspoon's can recall, a cover of the track, sang by Jewel, was featured in her 2002 movie of the same name.
The bash was clearly a blast, judging by the hilarious hashtags Hudson used to caption an Instagram collage of pics from the party.
"When you take a s**t load of pictures and you still don't have it perfect so you go for the ole collage post...." she wrote. "Happy Birthday gorgeous girl @reesewitherspoon !!! Love you #TequillaFirst #PostingLater #SaturdayNight#ImSoExcitedToGetIntoBedIDontEvenKnowWhatToDoWithMyself#NotWashingMyFace #GoodNight."
Hudson's Snapchat story -- which featured a ton of dancing and photos of the "bday babe" -- was just as epic.