Regina George is the (former) main antagonist of Mean Girls. She was the former Queen Bee of the school and the former leader of the Plastics.
She is portrayed by Rachel McAdams.
When Cady Herons (Lindsay Lohan) transferred from Africa, Regina quickly allowed Cady to the group and even set up some rules for her to follow and they quickly became friends.
In their first outing together, Regina invites Cady to go shopping with her, Gretchen Weiners, and Karen Smith. While they shop, Gretchen tells Regina her boyfriend Jason was going out with another girl, who was also in the mall, but she quickly came up with a plan to make her separate from him. She poses as a teacher through her cellphone, telling the girl's mom she did not pass her test, which prompts Jason to leave the girl. This makes Regina and Gretchen very happy.
She even introduced Cady the Burn Book, a journal which contains nasty insults about people, mostly girls, they come across. She later found out that Cady has a crush on her ex-boyfriend, Aaron and at the Halloween party, she kissed him in front of Cady. Cady in turn wanted to get revenge on her. Cady gave Regina a Kalteen bar which she claims will help Regina lose weight, but it really makes Regina gain weight. The Plastics turn their backs on Regina for Cady because Cady told Gretchen that Regina doesn't want to be her friend anymore. Regina found out that Cady was not being a good friend for not inviting her to the house party. Once Regina arrived and found Cady with Aaron, she stormed out while eating a Kalteen with her new boyfriend telling her what the bar really does.
Shocked, hurt, and upset, Regina decided to make Cady pay by framing Cady and the Plastics for writing down horrible things about each of the individuals and Regina even put down herself in the book so that she can make herself a victim. First, her plan was to go to the principal's office and tell him that she found the book in the girl's bathroom and she told him that Cady, Gretchen and Karen were responsible and they were sent to the office. Meanwhile, while classes were in progress, Regina made copies of the pages of the book and threw them all over the hallways and hid.