Is that you, Sienna Miller?!

The 33-year-old actress stepped out looking almost unrecognizable on the set of her new movie, Live By Night, in LA on Monday, Dec. 7.

sienna miller

Sienna in November 2015 (left) and filming Live By Night (right) in December 2015. (Photo Credit: Getty Images; Splash)

For her latest role, the mom-of-one was seen sporting bright red cheeks and lips as well as white-blonde, curly strands to portray Emma Gould, the floosie of Ben Affleck's character, Joe Coughlin, in the highly-anticipated 1920s crime film.

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The movie — scheduled to hit theaters in 2017 — is set in Boston during the prohibition era and also stars Zoe Saldana, Scott Eastwood and Chris Cooper.

Click through the gallery below to see more stars who’ve transformed themselves for movie roles!