The concept of sexuality shapes understandings of what it means to be human, what is considered normal or moral, and what is deemed deviant or immoral within specific social and historical contexts. Over the nineteenth, twentieth, and twenty-first centuries, it has been defined by political disputes and theoretical tensions, forming an interdisciplinary field that influences the recognition or marginalization of groups whose sexual practices are minoritized or pathologized. This chapter traces the concept’s trajectory within psychology and related disciplines. Research guided by ethical principles remains essential to advancing scientific and democratic debates on sexualities. In psychology, discussions of sexualities articulate diverse theoretical frameworks and research approaches, opening distinct fields of intervention and professional practice in response to contemporary social challenges.