1. Charlize Theron

It's hard to imagine Charlize Theron looking anything less than flawless. But, when she played serial killer Aileen Wuornos in the 2003 drama Monster, Charlize looked nothing like herself. For the role, she gained 30 pounds and hid behind splotchy makeup and prosthetic teeth. Charlize took home the Best Actress Oscar for her work and was back in shape in no time. She's definitely had one of the best transformations but there are so many more!

2. Christian Bale

Christian Bale shed 63 pounds from his 6-foot frame for the dark 2004 drama, The Machinist. He was pretty much unrecognizable! It just goes to show how committed he really is to his craft. After that role, he regained the weight (plus an extra 40) to play Bruce Wayne in Batman Begins. "I had to put on the weight pretty fast and it's not very healthy doing that," he's said. "I did actually start to feel I was putting my body under too much pressure, because I put on 100 pounds in five months."

3. Nicole Kidman

For her role as Virginia Woolf in 2002's The Hours, Nicole Kidman lost some weight and donned a prosthetic nose. She even bagged a Best Actress Oscar for her troubles.

4. Hilary Swank

Hilary Swank was only 24 when she portrayed Brandon Teena, a woman living as a man, in the 1999 film Boys Don’t Cry. Her intense preparation for the role even won her The Best Actress Oscar. She revealed to the New York Times, "Once I got into it, I was fully there. I felt like I lost every ounce of my femininity."

5. Renee Zellweger

Petite movie star Renee Zellweger put on 20 pounds to play Bridget Jones in 2001’s Bridget Jones’s Diary. When asked about all the overeating she had to do, she said, "It doesn't feel good, and no one wants to hear that, but it's the truth." Renee didn’t put herself through this craziness just once; she did it again for the 2004 sequel!

6. Matthew Mcconaughey

McConaughey's transformation for Dallas Buyers Club has been one of the most talked about transformations! Famous for his chiseled physique, the actor toned it down by losing 50 pounds! Matthew says his initial goal was 145 pounds, but when he hit that goal, he hadn't achieved the hollow, skinny look he was shooting for. “When I hit 135 lbs. I ran into somebody and they didn't just ask if I was all right, they said, ‘My God, we need to get you some help.’ And I thought, ‘There we go. That's the perfect spot.’”

7. Rooney Mara

In order to play tough girl Lisbeth Salander in the American version of The Girl with the Dragon Tattoo, girly-girl Rooney Mara butchered her hair, bleached her eyebrows, and pierced her nipple, nose, and eyebrow. Wow. "The eyebrows were the biggest shock because that really changed my face, and I didn't recognise myself," she told Vogue. "But I was fine because I knew it was going to be really helpful for getting into character." Her performance in the movie landed her her first Golden Globe nomination!

Well, there you have it. These are just seven out of many celebrities that had a major transformation for a movie role. It's all worth it in the end, right? Who do you think had the best transformation?