The desire to belong has been conceptualized by motivational psychologists as a fundamental human motive (need to belong), which means that it can guide thoughts, feelings, and behavior. Indeed, a growing literature has documented that students who perceive a sense of belonging in school generally fare well--academically, socially, and emotionally. In this article, we bring the racial/ethnic context to the study of school belonging. We review a number of studies from our program of research--both cross-sectional and longitudinal--that describe how feelings of belonging are shaped by important racial/ethnic context variables such as the size of one's racial/ethnic group in school across critical school transitions, perceived representation of one's group in critical STEM courses (e.g., 9th-grade math), and how the differences between school-level and course-level representation affect both schools belonging and academic achievement. We make an argument for studying racial/ethnic diversity as a fluid and dynamic construct that impacts motivation and achievement in previously understudied ways.