Serious actors often have to undergo radical transformations for certain roles, including shaving their heads and losing most, if not all, of their hair.Stars like Tom Cruise, Angelina Jolie, Aaron Paul, and Joey King have all shaved their heads for film or TV projectsrendering them unrecognizable in some cases.Whether it's playing a cancer patient or a prison inmate, these stars weren't afraid to lose their hair for a role.Some even shaved their heads on camera, with only one take to get it right.Visit Insider's homepage for more stories.Celebrities are no strangers to undergoing radical transformations for certain roles, including shaving their heads and losing most, if not all, of their hair.Whether they're playing an astronaut, a criminal, or a cancer patient, stars like Joseph Gordon-Levitt, Tom Cruise, and Angelina Jolie have all shaved their heads for a role.And some, like Gordon Levitt in "50/50" or Natalie Portman in "V For Vendetta," even shaved their heads on camera, with only one crucial take to get it right.While most celebrities tend to let their hair grow back out after filming, some have continued to keep a short cut even after the project has wrapped.Here are 21 actors who've shaved their heads for roles.Keanu Reeves went short for his role in the 1994 film "Speed."Reeves played an LAPD detective in the action film, which also starred Sandra Bullock and Dennis Hopper.Read more: Sandra Bullock admitted she had a crush on 'Speed' costar Keanu Reeves, and the actor just confirmed it was mutualNatalie Portman famously shaved her head onscreen in 2005's "V for Vendetta."Portman played Evey Hammond, a working class citizen caught up in an anarchist uprising.For the ending of 2002's "Minority Report," Tom Cruise went completely bald.The film is based on a short story, and stars Cruise as a futuristic police chief.For her role in the Broadway play "Wit," Cynthia Nixon shaved her head.Nixon played a cancer patient, and received rave reviews for her performance in 2012.In 2013's "Elysium," Matt Damon shaved his head completely.The sci-fi film is set in 2154, and focuses on the efforts of Damon's terminally ill character to reach a powerful spaceship in Earth's orbit.Cate Blanchett ditched most of her hair for her role in 2002's "Heaven."Blanchett loses her hair towards the end of the film, after her character commits a murder and flees Italy.Demi Moore was nearly unrecognizable after she shaved her head for 1997's "G.I. Jane."Moore's character underwent grueling military training in the film, and the actress shaved her head on set to get into her character's mindset.Joseph Gordon-Levitt played a cancer patient in 2011's "50/50."The experiences of Gordon-Levitt's character in the film are based on the real-life battle screenwriter Will Reiser fought with cancer.Charlize Theron played Furiosa in the 2015 film "Mad Max: Fury Road." Theron shaved her head for the role, which saw her play a rebellious lieutenant in a post-apocalyptic society. James Franco shaved his head for "Zeroville," a dramedy set in the 1970s.Franco's character, a pop culture junkie, even has tattoos of Montgomery Clift and Elizabeth Taylor on the back of his shaved head.To play Gypsy Rose Blanchard in "The Act," Joey King shaved her head completely.On "The Act," King plays real-life criminal Gypsy Rose, who was convicted of second-degree murder after helping to murder her mother. Gypsy's mother famously made it appear as though her daughter was seriously ill, when she was, in fact, perfectly healthy.In 2016's "Split," James McAvoy plays a character with multiple personalities.McAvoy's character has 23 separate personalities in the filmsome of them more dangerous than others.Millie Bobby Brown's character on "Stranger Things" had a shaved head on season one.Brown's character, Eleven, was used as a test subject by a secret government agency, but escapes in the first season.Read more: Millie Bobby Brown expertly shut down critics telling her to 'act your age' after the 14-year-old posed for a photo wearing a snakeskin dress and heelsCara Delevingne shaved her head for "Life in a Year."The 2018 film sees Delevingne play a cancer patient with a terminal diagnosis.On "The Night Of," Riz Ahmed's character Naz shaves his head after being incarcerated.Ahmed told Vanity Fair that he visited Rikers Island and New York City courtrooms to prep for his role on the hit HBO show.In 2018's "Where Hands Touch," Amandla Stenberg's character is sent to a concentration camp.Like many of the real-life prisoners in Nazi camps, Stenberg's character is forced to cut her hair short upon entry.Anne Hathaway's long hair was famously chopped short during a scene in 2012's "Les Misrables."Hathaway's hairdresser Paul Gooch actually put on a costume to play the "hair crone" who snips Fantine's tresses during the tense scene.To play supermodel Gia Carangi in 1998's "Gia," Angelina Jolie sported a super-short cut.Carangi rose to fame in the early 80s, but died from AIDS-related complications after a very public struggle with drug addiction.In 1992's "Alien 3," Sigourney Weaver's character Ripley has short hair.Ripley crash lands on a penal colony in the third "Alien" film, and ultimately sacrifices herself to save humankind at the end of the film.To play drug kingpin and high school teacher Walter White on "Breaking Bad," Bryan Cranston had to keep his head shaved.Cranston's character becomes a drug dealer and eventual kingpin after being diagnosed with terminal lung cancer.Aaron Paul also had a shaved head for some of "Breaking Bad," and reprised the look for "El Camino."Paul played Jesse Pinkman, a confidant and later victim of Walter White, on the show and subsequent movie.Read more: 29 details you may have missed in Netflix's 'Breaking Bad' movie Click here to read full news..