Defining Male and Female Act of 2025

This bill amends the U.S. Code to define key terms like "sex," "male," and "female" based on biological characteristics present at conception, specifically referencing reproductive anatomy. It requires all federal agencies, courts, and Congress to use these biological definitions when interpreting laws, regulations, or agency actions - replacing current interpretations that consider gender identity. The bill explicitly states that "gender identity" does not constitute a valid basis for determining sex under federal law. This change would directly affect how federal agencies implement existing laws related to healthcare, education, employment, and civil rights by mandating biological sex definitions in their operations.