It's hard to wrap our heads around the fact that Rachel McAdams is 36, given she hasn't aged in the past 10 years. But alas, our favorite 'Mean Girl' has crossed the threshold into her late-'30s.

But what we're really having trouble grasping is how The Notebook star is now the same age as THESE 8 celebrities!

Click through for the shocking truth — and happy birthday, Rachel!