Zellweger was born in Baytown, Texas and moved to Katy, Texas, a suburb of Houston, at the age of nine with her family. Her father, Emil Erich Zellweger, is a Swiss-born engineer who worked in the oil refining business, and her mother, Kjellfried Irene (nee Andreassen), is a Norwegian-born nurse and midwife. Zellweger was raised in a family of "lazy Catholics and Episcopalians". In high school, she was a cheerleader and gymnast, and participated in the drama club. She graduated from Katy High School in 1987. After high school, she went to the University of Texas at Austin to major in English. Though she took a drama class only because she needed a fine arts credit to complete her degree, it made her appreciate how much she loved acting. During this time, she supported herself by taking a series of jobs in Austin, Texas, including working as a waitress at a topless bar, an experience that she has said taught her as much as university did.

Film career

While still in Texas, Zellweger appeared in several films, including Return of the Texas Chainsaw Massacre. She subsequently moved to Los Angeles to pursue a career in acting, winning roles in the films Reality Bites, Empire Records, The Whole Wide World, and 8 Seconds. Zellweger first became widely known to audiences around the world with her role in 1996's Jerry Maguire, where she played the romantic interest of Tom Cruise's character. She won the role over Mira Sorvino and Marisa Tomei. Since then, Zellweger has won acclaim in roles such as One True Thing opposite William Hurt and Meryl Streep, and in Neil LaBute's Nurse Betty opposite Morgan Freeman. The role garnered the actress her first of three Golden Globe Awards, but she was in the bathroom when future co-star Hugh Grant announced her name. Zellweger later protested: "I had lipstick on my teeth!"

In 2001, Zellweger gained the prized lead role in the film Bridget Jones's Diary, amid much controversy since she was neither British nor overweight. During casting Zellweger was told she was too skinny to play the chubby Bridget, so she very quickly embarked on gaining the required weight. Her dramatically personal yo-yoing weight has been the subject of much media interest. As well as receiving voice coaching to fine-tune her English accent, part of Zellweger's preparations involved spending three weeks working undercover in a "job experience placement" for British publishing firm Picador in Victoria, London. As a result of her considerable efforts to effect author Helen Fielding's character, Zellweger caught the attention of the Academy of Motion Picture Arts and Sciences, and received her first Best Actress Academy Award nomination.

In 2002, she starred with Michelle Pfeiffer in White Oleander and in Rob Marshall's Best Picture winning film Chicago opposite Catherine Zeta Jones, Richard Gere, Queen Latifah, and John C. Reilly. Zellweger earned her second Academy Award nomination as Best Actress, as well as the Screen Actors Guild and Golden Globe Award. In 2004, Zellweger finally received an Academy Award, this time as Best Supporting Actress in Anthony Minghella's Cold Mountain opposite Jude Law and Nicole Kidman. Zellweger has since starred in the sequel to Bridget Jones' Diary in Bridget Jones: The Edge of Reason, lent her voice to the animated feature Shark Tale, and starred in the 2005 Ron Howard film Cinderella Man opposite Russell Crowe and Paul Giamatti. On May 24, 2005, Zellweger received her star on the Hollywood Walk of Fame. Her most recent film is Miss Potter, based on the life story of acclaimed author Beatrix Potter, with Emily Watson and Ewan McGregor, released in December 2006.

Zellweger and Marc Forster, took part in the 2005 HIV prevention campaign of the Swiss federal health department. Zellweger was the subject of an Israeli pop song Renee by Ariel Horowitz, where Horowitz describes his love to Zellweger, and says that he would like to marry her and bring her back to Israel with him.