In Brazil, legal and political discussions on childhood and adolescence are usually guided by the ideal of pure, innocent, and vulnerable girls. This construction has historically served to both censor the exercise of child and adolescent sexual agency and legitimize the exclusion of unruly girls who do not correspond to the envisioned profile that should be protected. That is the case for Brazilian young wives, a large but invisible group of girls continuously neglected by child protection discourses, services, and policies in the country. This paper aims to introduce and explore the current scenario of child marriage in Brazil by overviewing the national legal norms surrounding the practice, summarizing two relevant locally produced qualitative research on the subject, carried out by Instituto Promundo and Plan International Brasil, analysing available national quantitative data on the extent and key characteristics of early marriage, specifically IBGE's 2010 Demographic Census and 2021 Civil Registry Statistics, and problematizing what is understood as the young wives' agency. Its main proposition is that a more nuanced, dynamic, and critical understanding of children's agency is needed for truly comprehending the practice of child marriage in Brazil and developing public services and policies that both prevent it and aid young wives in their daily lives.