In this chapter, we summarize and integrate some of the latest developmental science research on gender stereotypes and discrimination in childhood and adolescence. We focus on five forms of sexism: (a) stereotypes and discrimination against boys regarding their school behaviors and disciplinary actions; (b) stereotypes and discrimination against girls in science, technology, engineering, and mathematics (STEM) domains; (c) stereotypes and discrimination in sports; (d) peer gendered harassment, including sexual harassment and teasing because of gender atypicality or nonconformity; and (e) sexualized gender stereotypes that sexually objectify girls and assume boys are sexually voracious. First, we document each type of sexism and examine children's awareness and perceptions of that bias, including their own self-reports and attributions. We examine the implications of this sexism for children and adolescents' developmental health (i.e., social, academic, and psychological well-being). We then draw connections between these various areas of research, focusing on how these different forms of sexism interact to reduce equity and justice among children and negatively impact positive developmental outcomes. The chapter concludes with suggestions for future research.