Judith Butler is an influential American philosopher and gender theorist known for her work on gender identity and sexuality. She gained prominence with her book, Gender Trouble, published in 1990, where she argues that gender is not a fixed trait but rather a performance shaped by societal norms. This idea has significantly impacted feminist theory and LGBTQ+ studies. Butler's theories challenge traditional views of gender, suggesting that it is constructed through repeated actions and behaviors. Her work encourages people to think critically about how identities are formed and the ways in which power dynamics influence our understanding of gender and sexuality.