- Thora Birch was born on March 11, 1982 in Los Angeles.
- She is the eldest child of Jack Birch and Carol Connors, who have been her business managers throughout her acting career, and are former adult film actors who both appeared in supporting roles in Deep Throat (1972).
- Birch is of German Jewish, Scandinavian and Italian ancestry.
- The family's surname was originally "Biersch," coming from their German Jewish ancestors.
- Her name, Thora, is derived from the name of the Norse god of thunder and lightning, Thor, and she has a younger brother named Bolt.
- She made her film debut in the 1988 science-fiction comedy Purple People Eater, for which she won a Youth In Film Award and a Young Artist Award in the category of "Best Young Actress Under Nine Years of Age".
- She got her first role at the age of 6 in the short-lived sitcom Day by Day (1988).
- Was actually only 16 years old at the time she was filmed nude for a scene in American Beauty (1999).
- Used to live on her family ranch in East Los Angeles where she finished high school through a computer-based correspondence course.
- Has a Green Belt in Karate.
- Thora Birch is a vegetarian.
- Does her own stunts.