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Drop the mic! Reese Witherspoon takes the stage at star-studded 40th birthday bash

Reese Witherspoon knows how to party, and we've got the proof!
/ Source: TODAY

Reese Witherspoon knows how to party, and we've got the proof!

Witherspoon turns 40 Tuesday, but she didn't wait for the big day to kick off the fun. Instead she gathered with family, friends and famous faces Saturday night for a celebration to remember — and share on social media.

As for the entertainment, the "Sweet Home Alabama" star took the stage herself alongside pal Keith Urban and belted out that Lynyrd Skynyrd classic.

Vanity Fair's Derek Blasberg posted a short clip from the performance on Instagram and wrote, "You can take the girl out the South, but you can't take Sweet Home Alabama out the girl!

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Kate Hudson shared a college of shots from the bash, showing just how many blonde BFFs the "Legally Blonde" actress has. The answer? A lot.

But it was Hudson's selection of hashtags that really revealed how much fun the friends were having: "#TequillaFirst #PostingLater #SaturdayNight #ImSoExcitedToGetIntoBedIDontEvenKnowWhatToDoWithMyself #NotWashingMyFace #GoodNight"

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Partygoers seen in some of the pics also include Laura Dern and Taylor Swift. The pop star took the mic for some off-camera entertainment later in the evening, too.

According to People, Nicole Kidman, Matthew McConaughey, Robert Downey Jr., Tobey Maguire, Jennifer Aniston, Justin Theroux and Courteney Cox were also on hand for the fun.

But the biggest VIP — as far as Witherspoon is concerned — could be seen in a pre-party video: her mom, Betty!

"You gonna get crazy on the dance floor, Mom?" the actress asked in the clip.

"Crazy," her mother assured her.

Follow Ree Hines on Twitter.