Megan Fox is of Irish, French and Native American ancestry, and was born in Oak Ridge, Tennessee to Darlene and Franklin Fox. She was raised Roman Catholic and attended Catholic school for 12 years. Fox's parents divorced when she was young and she and her sister were raised by her mother and her stepfather, Tony Tonachio. She said that the two were "very strict" and that she was not allowed to have a boyfriend or invite friends to her house. She lived with her mother until she made enough money to support herself.
Megan Fox began her training in drama and dance at age five, in Kingston, Tennessee. She attended a dance class at the community center there and was involved in Kingston Elementary School's chorus and the Kingston Clippers swim team. At 10 years of age, after moving to St. Petersburg, Florida, Fox continued her training. When she was 13 years old, Megan Fox began modeling after winning several awards at the 1999 American Modeling and Talent Convention in Hilton Head, South Carolina. At age 17, she tested out of school via correspondence in order to move to Los Angeles.
Megan Fox has spoken extensively of her time in education; that in middle school she was bullied and picked on and she ate lunch in the bathroom to avoid being "pelted with ketchup packets". She said that the problem was not her looks, but that she had "always gotten along better with boys" and that "rubbed some people the wrong way". Megan Fox also said of high school that she was never popular and that "everyone hated me, and I was a total outcast, my friends were always guys, I have a very aggressive personality, and girls didn’t like me for that. I’ve had only one great girlfriend my whole life". In the same interview, she mentions that she hated school and has never been "a big believer in formal education" and that "the education I was getting seemed irrelevant. So, I was sort of checked out on that part of it".
At 16, Megan Fox made her acting debut in the 2001 film Holiday in the Sun, as spoiled heiress Brianna Wallace and rival of Alex Stewart (Ashley Olsen), which was released direct-to-DVD on November 20, 2001. In the next several years she guest-starred on What I Like About You and Two and a Half Men, as well as being an uncredited extra in Bad Boys II (2003). In 2004, she made her film debut in Confessions of a Teenage Drama Queen co-starring opposite Lindsay Lohan, playing the supporting role of Carla Santini, a rival of Lola (Lohan). Fox was also cast in a regular role on the ABC sitcom Hope & Faith, in which she portrayed Sydney Shanowski, replacing Nicole Paggi. Megan Fox appeared in seasons 2 to 3, until the show was cancelled in 2006.
In 2007, Megan Fox won the lead female role of Mikaela Banes in the 2007 live-action film Transformers, based on the toy and cartoon saga of the same name. Fox played the love interest of Shia LaBeouf's character Sam Witwicky. Fox was nominated for an MTV Movie Award in the category of "Breakthrough Performance", and was also nominated for three Teen Choice Awards. Fox had signed on for two more Transformers sequels. In June 2007, Fox was cast in a minor role in How to Lose Friends & Alienate People, starring alongside Jeff Bridges, Simon Pegg and Kirsten Dunst. She portrayed Sophie Maes, a love interest of Sydney Young (Simon Pegg). The film premiered on October 3, 2008, but was considered a box-office failure.
Megan Fox reprised her role as Mikaela Banes in the Transformer sequel, Transformers: Revenge of the Fallen. There was some controversy surrounding Fox's appearance while filming the sequel of Transformers when Michael Bay, the film's director, ordered the actress to gain 10 pounds. The film was released worldwide on June 24, 2009. Fox was to star in the third installment, Transformers: Dark of the Moon, but was not included because of her statements comparing working under director Bay to working for Hitler (see below). Co-star Shia LaBeouf said, "Criticism is one thing. Then there's public name-calling, which turns into high-school bashing. Which you can't do." Bay similarly amended his previous statements of support of Fox, and told GQ in June that Megan Fox was fired on orders of executive producer Stephen Spielberg.
In between Revenge of the Fallen and Dark of the Moon, Megan Fox had her first lead role playing the title character in Jennifer's Body, written by Academy Award-winning screenwriter Diablo Cody. She played Jennifer Check, a mean-girl cheerleader possessed by a demon who begins to feed off the boys in a Minnesota farming town. The film was released on September 18, 2009, and co-stars Amanda Seyfried and Adam Brody.
In early April 2009, Megan Fox signed on to star as the lead female role in the upcoming 2011 film The Crossing, about a young couple who get caught up in a drug trafficking scheme during their vacation to Mexico. In March 2009, Variety reported that Fox was set to star as the lead role of Aspen Matthews in the film adaption of the comic books Fathom which she will also co-produce with Brian Austin Green. Fathom is currently in pre-production. Megan Fox appeared with Dominic Monaghan in the music video for Eminem and Rihanna's single "Love the Way You Lie".