Kate Box

Bosworth's first film role came after an open casting call in New York for the supporting part of Judith in the 1998 film, The Horse Whisperer. The film's producers needed someone who was already an experienced horse rider, leading to Bosworth's successful audition for the role. The film received positive reception from film critics. In 2000, she starred in the television series drama Young Americans, in which she played Bella Banks. The series, however, was canceled. That same year, she had a small part in the film Remember the Titans. In 2001, Bosworth moved to Los Angeles in hopes of obtaining easier access to auditions and better film parts.

Bosworth was accepted to Princeton University in late 2000, but because of continual deferral of her attendance, her acceptance was revoked. She is a member of the Appalachia Service Project.

Bosworth developed an interest in equestrian sports, specifically stadium jumping, and by the age of fourteen, she was a champion equestrian. She graduated from Cohasset High School, in Cohasset, Massachusetts, in 2001.

The breakthrough role in Bosworth's career came in the 2002 surfing movie Blue Crush, which she prepared for by working out with two separate trainers seven hours a day for months in order to add fifteen pounds of muscle to her frame. In his review of the film, Rolling Stone's Peter Travers wrote: "Bosworth is a star in the making, but even she can't outshine the surfing footage, which is flat-out spectacular." The film received positive reviews and grossed $40 million at the United States box office. Following the success of Blue Crush, Bosworth took on the lead role in low-budget Wonderland (2003) opposite Val Kilmer. Bosworth played the teenage girlfriend of porn star John Holmes.

In 2004, she played the lead role in romantic comedy Win a Date with Tad Hamilton!, opposite Topher Grace. The film was critically and financially unsuccessful. Also in 2004, Bosworth depicted actress Sandra Dee in Beyond the Sea. The movie received mixed reception, and was a box office disappointment, though Bosworth received critical acclaim for her performance. The following year, Bosworth portrayed Chali, a Hare Krishna, in the film adaptation of Myla Goldberg's novel Bee Season (2005), about a dysfunctional Jewish family. She has appeared in several Revlon ads and ranked as number 60 in FHM's "100 Sexiest Women in the World 2005" list. For two years running, she has placed on the Maxim Hot 100 List – number 38 in 2005 and number 8 in 2006.

Bosworth was cast as reporter Lois Lane in Bryan Singer's superhero film Superman Returns (2006). She starred along with her Beyond the Sea co-star Kevin Spacey as Lex Luthor, as well as newcomer Brandon Routh as Superman. The film was a box office success and received mostly positive reviews. Bosworth's performance however, was not well received among critics; Anthony Lane of The New Yorker noted, "The new Lois Lane, Kate Bosworth, is not a patch on Margot Kidder, or, for that matter, on Teri Hatcher, in the TV series." San Francisco Chronicle film critic Mick LaSalle felt that Bosworth, at the age of 22 years, was too young to portray Lois Lane, and the climax did not "match the potential of the tiring 154 minute long film". Although Bosworth's performance was ambivalently received, she herself loved the experience of working on the movie. As she told Teen Vogue in August 2006, "You know how you have an experience, a time in your life when you feel you've come into your own? When you grow up a bit, and think, Now I get it? [...] That's how I feel. I feel a little bit more complete." The movie grossed $52 million during its opening weekend in North America and went on to earn $391 million worldwide.

In 2006, she optioned the film rights to Catherine Hanrahan's novel Lost Girls and Love Hotels and was set to produce the project alongside filmmaker Nadia Connors. As of 2016, the project was at a standstill. In 2010, she starred in The Warrior's Way, which was shot in New Zealand alongside Korean actor Jang Dong-gun and Geoffrey Rush. The film was one of 2010's biggest box office flops, grossing only slightly more than $11,000,000 worldwide, but costing $42 million. She has said about her roles, "I just don't do comfort zones."

Bosworth starred as Louise in the psychological drama called The Girl in the Park with Sigourney Weaver, Alessandro Nivola and Keri Russell, written and directed by Pulitzer Prize winner David Auburn in his directorial debut. The film premiered at the 2007 Toronto International Film Festival, it has since been picked up by The Weinstein Company. Alissa Simon of Variety wrote that Bosworth "tries her best, but her character's too extremely drawn." Bosworth also filmed 21, an adaptation of the book Bringing Down the House, in early 2007 in Boston, Massachusetts and Las Vegas, Nevada. This film reunites her with co-star Kevin Spacey and director Robert Luketic. 21 garnered mixed reviews, with Joanne Kaufman of the Wall Street Journal concluding, "Very little adds up in 21."

In January 2008, Bosworth was named the new face for Calvin Klein Jeans and was featured in Calvin Klein Jeans campaigned. She also took on the role of spokesperson for the American luxury bag brand Coach in Asia.

Bosworth designed a jewelry line with friend and celebrity stylist Cher Coulter called JewelMint, which launched in October 2010. JewelMint, the first vertical of MySpace co-founder Josh Berman and Diego Berdakin's social commerce company, BeachMint, has designs by Coulter and Bosworth.

In 2011, Bosworth contracted to sing the television jingle for Cotton Incorporated's "Fabric of My Life" advertisement. On December 4, 2012, Topshop revealed that Bosworth was the "secret" woman in the new Topshop Christmas Adverts.

In mid-2011, Bosworth began dating American director Michael Polish, whom she had met earlier that year when he directed her in the film Big Sur. Bosworth and Polish announced their engagement in August 2012, and married on August 31, 2013 in Philipsburg, Montana.

In 2013, Bosworth was cast in the horror film Before I Wake. The film was directed by Mike Flanagan and it was released on Netflix in 2017.

In 2016, Bosworth was cast in the post-apocalyptic horror film The Domestics. The film was released on June 28, 2018.

In September 2018, it was announced that Bosworth was cast in the main role of KC on the Netflix science fiction miniseries The I-Land. The miniseries was released on September 12, 2019. In the same year, Bosworth was cast in the sci-fi thriller Genesis.

In 2018, Bosworth was included in People magazine's list of 25 Women Changing the World. In late 2018, Bosworth and her husband, Michael Polish, debuted the film that they privately funded called Nona. The film focuses on the issues of human trafficking. She works closely with CAST, the Coalition to Abolish Slavery and Trafficking.