Larson was born Brianne Sidonie Desaulniers on October 1, 1989, in
Sacramento, California, to Heather and Sylvain Desaulniers.
[1][2] Her parents were
homeopathic chiropractors who ran a practice together, and they have another daughter, Milaine.
[3][4] Her father is
French Canadian and in her childhood, Larson spoke French as her first language.
[5] She was mostly
homeschooled, which she believed allowed her to explore innovative and abstract experiences.
[3][6][7] Describing her early life, Larson has said that she was "straight-laced and square", and that she shared a close bond with her mother but was shy and suffered from social anxiety.
[3][6][8] During the summer, she would write and direct her own home movies in which she cast her cousins and filmed in her garage.
[9] At age six, she expressed interest in becoming an actress, later remarking that the "creative arts was just something that was always in me".
[3][10] That same year, she auditioned for a training program at the
American Conservatory Theater in San Francisco, where she became the youngest student admitted.
[4][11]
Larson experienced trauma when her parents divorced when she was seven.
[11] She had a dysfunctional relationship with her father; she has recalled, "As a kid I tried to understand him and understand the situation. But he didn't do himself any favors. I don't think he ever really wanted to be a parent."
[11] Soon after their split, Heather relocated to Los Angeles with her two daughters to fulfill Larson's acting ambition. They had limited financial means and lived in a small apartment near Hollywood studio lots at
Burbank.
[11] Larson described her experience, "We had a crappy one-room apartment where the bed came out of the wall and we each had three articles of clothing."
[3] Even so, Larson has recounted fond memories of that period and has credited her mother for doing the best she could for them.
[12]
As her last name was difficult to pronounce, she adopted the stage name Larson from her Swedish great-grandmother as well as an
American Girl doll named
Kirsten Larson that she received as a child.
[10][13][14] Her first job was performing a commercial parody for
Barbie, named "Malibu Mudslide Barbie", in a 1998 episode of
The Tonight Show with Jay Leno.
[2][6][15] She subsequently took on guest roles in several television series, including
Touched by an Angel and
Popular.
[4] In 2000, she was cast in the
Fox sitcom
Schimmel, which was canceled before airing when its star,
Robert Schimmel, was diagnosed with cancer.
[16][17][18]