Hollywood actresses always seem to look so glamorous. They are very lucky to have a team of hairstylists, makeup artists and fashion designers to make sure that they always look their best. They often have personal trainers to keep them in shape and somehow manage to appear nearly perfect on the red carpet. Most women in Hollywood take on roles in films that show them in their best light.

Yet, there are those female celebs who are willing to sacrifice their beauty to enhance their character in a movie. These brave women cut their lovely locks, remove their makeup and get down to the nitty-gritty of their craft. They don’t rely on their good looks to carry a role and are transformed into totally different people.

Some of these performances earned these ladies an Oscar or various other awards. We delved deep into the process to find out just what it took to morph these actresses into totally new people. From serious workout regimes to a complete loss of their own vanity, it’s amazing to discover the lengths these women went to for their craft.

Please enjoy this list of 20 times we didn't recognize beautiful celebrities.

20 Nicole Kidman: The Destroyer

Fans hardly recognised Nicole Kidman when she morphed into the character Erin Bell for the film, The Destroyer. She plays an aging cop whose past catches up with her. Kidman’s transformation took her from a glamorous actress to a total plain Jane.

According to Daily Trojan, Nicole discussed her role in a Q&A session, saying, “As an actor, I want to become different people. It starts internally and then, once you understand the history and the life story of the character, how does that change the way you walk, move, your skin, your eyes, all of it.”

19 Charlize Theron: Monster

There’s no denying that Charlize Theron is one of the most beautiful actresses in Hollywood. She underwent a transformation to become Aileen Wuornos for the movie, Monster. The role landed her an Oscar in 2004 and she used a strange inspiration to portray the character: she focused on her exterior to display her character's inner turmoil.

"In court, she was kind of like a blow fish. She blew herself up in order to survive," Theron said of Wuornos, as Today reports. She added, "The greatest thing I can hope for, which is an impossible thing to hope for because so much emphasis has been put on the transformation, [is] that people can go see it and get past all that.”

18 Mariah Carey: Precious

Mariah Carey may be known as a diva but she totally toned down her look for her role in the movie Precious. She took on the role of Ms. Weiss, a social worker who was much less alluring than the singer. According to Ace Showbiz, Carey opened up about the entire process.

"It's a whole thing, but Lee Daniels is a bonafide genius so I put myself in his hands. And he was like, 'No makeup. We're going to put dark stuff under your eyes. Your hair is going to be cut and short and brown. And you're gonna wear big clothing and it's going to be a whole thing.' "

17 Jennifer Aniston: Cake

Jennifer Aniston took a break from being America’s sweetheart to take on a gritty role in the movie Cake. The actress was best known as Rachel Green on the show Friends but she wanted to branch out. The Hollywood Reporter caught up with Aniston and asked her if she was worried the media would dislike her for undergoing a make-under for the role.

“I didn’t even think about that. That was honestly, just, who she is. This woman would never wear a stitch of makeup. There [are] women who wear makeup and [those] who go without makeup. That’s not ever been my thing, like, "a beauty icon," you know?”

16 Cameron Diaz: Being John Malkovich

Cameron Diaz was almost unrecognizable as the character Lotte in the film, Being John Malkovich. Filmmaker magazine asked Spike Jonze about how he and Diaz constructed the look. “I showed her pictures – I take a lot of pictures of people, just driving around the street, and I get wardrobe and character ideas from that,” he said, adding,

“We wanted Craig and Lotte to be a struggling artist couple living in Brooklyn. You know how couples end up looking alike after they’ve been together for a while? I wanted them to look a little similar, and that’s where the [frizzy] hair came from.”

15 Renée Zellweger: Bridget Jones

Renée Zellweger changed her looks for her role in Bridget Jones: The Edge of Reason. The character was dowdier than the actress is in real life. When Zellweger returned to play the role in the sequel, Bridget Jones's Baby, there was less emphasis put on her original looks.

According to USA Today, Zellweger discussed what inspired the difference in the look of Bridget Jones. “It was director Sharon Maguire who pushed that plot point,” she said. “Sharon’s explanation was, 'Let’s let her have this thing that she’d always hoped to achieve in her life, and yet show how little consequence it has on her happiness.”

14 Rosamund Pike: 7 Days In Entebbe

Rosamund Pike had a major make-under for the film, 7 Days In Entebbe. The usually blonde actress appeared in the film with dark hair and wore minimal makeup. Slant  magazine interviewed Pike and asked her why director Scott Cooper chose to cast her in the film.

“I think he was looking for the ability to be completely unvain and physical and express things—yeah, I guess a feral intensity," she continued. "And I’m definitely being drawn recently to being not just a face, but being a body. The physical nature of film has become much more open to me.”

13 Shailene Woodley: Adrift

Shailene Woodley had to go to drastic measures to prepare for her role in the movie Adrift. The actress played a woman who's lost at sea with her husband for 41 days and the part required serious physical strength. Fans thought that Woodley was hardly recognizable in the film.

She opened up to Livestrong about her rigorous training, saying,

“Sailing looks very romantic and it looks very easy because good sailors make it look easy, but it’s actually quite difficult and requires a lot of upper-body strength, which I didn’t have. So our training was mostly focused on upper-body building.”

12 Vanessa Hudgens: Gimme Shelter

Vanessa Hudgens may be best known for her role in High School Musical but the actress took a departure from that for the movie Gimme Shelter. She admitted to E! News that she actually enjoyed letting herself go a bit, saying,

“I cut off all my hair, which really set the tone. It was such a liberating thing and kinda reminded me—if I can do that, I can do this. I wanted her to be strong and tough but broken because that's what she is. You just see her transform into someone who actually finds love and really feels it for the first time and there's nothing more powerful than finding love."

11 Emma Stone: Billie Jean King

Emma Stone totally changed her physique when she took on the role of Billie Jean King. The movie was based on the life of a tennis great and Stone had to work hard get her body toned for the part. Her trainer, Jason Walsh, spoke with Well and Good about their goals for the character and how Stone achieved them.

“My focus was to give her that athletic prowess and resiliency and get her feeling comfortable in her own skin on the court,” Walsh said. “There’s nothing I like more than empowering women so they feel powerful and confident onscreen.”

10 Anne Hathaway: Les Misérables

Anne Hathaway morphed into the character Fantine in the movie version of Les Misérables. The actress was so committed to the part that she made the decision to actually cut her own hair into the now famous buzzcut. Hathaway opened up to Indie Wire about the experience.

“I offered [director Tom Hooper] the option of cutting my hair,” she said. “It’s such a devastating scene in the book, I thought doing it for real might raise the stakes a bit for the character.”

Well, she must have made the right choice because she won an Oscar for Best Supporting Actress in 2013.

9 Rooney Mara: The Girl With The Dragon Tattoo

Rooney Mara completely changed her look for the film, The Girl With The Dragon Tattoo. The actress underwent a total makeover for the movie and spoke with Vogue about the intense steps she went through to become Lisbeth Salander.

“[Hairstylist] Danilo cut my hair, shaved the sides, bleached the eyebrows, then dyed my hair black,” Mara said. "Then we went and did the piercings—all in one day. The eyebrows were the biggest [surprise] because that really changed my face, and I didn’t recognize myself. But I was fine because I knew it was going to be really helpful for getting into character.”

8 Tilda Swinton: Snowpiercer

Tilda Swinton has changed her looks for many movies but none were as dramatic as the lengths she went to for her part in Snowpiercer. Yahoo reports what she had to say about the creative process behind becoming Mason.

“I always wanted to play a character with a nose like that because of what it does to the eyes, actually,” Swinton said. “So we got a piece of sellotape and put my nose up, and then we thought, “Oh, well, then maybe I’d better have some teeth.” So we wrote it down, “Let’s get some teeth.” What about some googly glasses? What about a wig that kind of moves around?”

7 Halle Berry: Monster's Ball

Halle Berry made history when she was the first African American woman to win an Oscar for her role in the film Monster’s Ball. It was a well-deserved win because she was willing to lose herself in the character. She spoke with the blog The Hollywood Interview about what sort of research that went into becoming Leticia. She said,

“There was no real research. It was really just discovering how she lived in me and discovering things in my own life or my own experience to help bring the colors to her. So that was really my work as an actress - trying to figure out the nuances of her.”

6 Emma Thompson: Nanny McPhee

Emma Thompson may be known for winning Oscars and her more dramatic roles but one of her most memorable characters is Nanny McPhee. She dressed up as the larger-than-life nanny and spoke with She Knows about what it was like underneath the costume and heavy makeup. She said,

“You’ve got on a prosthetic nose so you can’t really breathe... You have to be rather Zen when you’re in that state. You have to let it float over you. It’s very uncomfortable. It takes about an hour-and-a-half to put all of that on.”

5 Mo'Nique: Precious

Mo’Nique’s performance in the movie Precious earned her an Oscar and we think that her stripped-down look has everything to do with her triumph. The comedian was known for making people laugh but she transformed into a totally different person for this role. CBS News sat down with Mo’Nique to find out how she would describe the experience.

“I was proud to be a part of something that is very honest, and Lee Daniels, baby, he's going to give it to you,” she said. “He's going to give it to you raw. No chaser, no lollipop licking, this is it. It's the dirt, it's the grime, it's what we're afraid of.”

4 Julie Roberts: Secrets In Their Eyes

Julia Roberts typically takes on charming roles that showcase her million-dollar smile. So, it was surprising to see her take on a dramatic character in the movie, Secrets In Their Eyes. The dynamic actress spoke with The New York Times about the transformation she underwent for the part.

“It needs to have impact,” Roberts said. “You need to see that the candle inside of someone has been extinguished. And I had some really specific ideas [for a pivotal scene that depicts that] and almost constructed Jess from that moment into the past. [The contacts were] like having Kleenex in front of my eyes. It was so hard to see with those things on.”

3 Drew Barrymore: Never Been Kissed

There are few actresses more spunky than Drew Barrymore so it was totally fun to watch her play the character of Josie Geller in the film Never Been Kissed. Interview spoke with the film's costume designer, Mona May, to uncover the creative force behind the character.

“Drew [Barrymore] is amazing, I’ve worked with her for many years—she’s so hands-on,” May said. “For Never Been Kissed we went to Loehmanns to try clothes on because she really wanted to find the coolest, weirdest stuff to create this character. She’s so strong in her visuals and how she likes things, so it was really us creating it together, which is always really fun.”

2 Sandra Bullock: Miss Congeniality

Sandra Bullock was hilarious in her role as Gracie in the Miss Congeniality movies. The stunning actress was made to look like a major tomboy at the beginning of the first film and she did a great job acting like an unkempt FBI agent. Bullock spoke with Black Film about what it was like to step into the character's shoes.

"I would like to be Gracie," she said. "I think that Gracie just can't help doing what she does. No matter how far away she gets from herself, she just ekes out. No matter how straight her hair is blown dry, that curly hair will ping out."

1 Demi Moore: G.I. Jane

Demi Moore took drastic steps to transform herself into her G.I. Jane character The gorgeous actress morphed into a bald powerhouse and, according to The Telegraph, she actually shaved her head while she was on the set of the 1997 film.

Moore had this to say about an unexpected effect the event had on her three daughters:

"I had more people want to touch me. The funniest responses came from my children, who would say to friends, 'Hey, do you want to come look at my mom's head?' as if I were a show-and-tell item."

References: She Knows, Vogue, Well and Good, E! News

Next 10 Surprising Facts About Elvis Presley