Brie Larson was born as Brianne Sidonie Desaulniers in Sacramento, California, to Heather (née Edwards) and Sylvain Desaulniers, homeopathic chiropractors who ran a practice together.

Larson expressed interest in becoming an actress and auditioned for a training program at the American Conservatory Theater in San Francisco, becoming its youngest student.

Larson's parents divorced, and she moved to Los Angeles with her mother and sister to pursue her acting career.

Larson was mostly homeschooled, which allowed her to explore innovative and abstract experiences and fostered her creativity.