Robert M. Sellers, PhD, most known for his influential and highly cited Multidimensional Model of Racial Identity (MMRI), is one of the most prolific and foundational Black scholars in psychology. From racial identity theory development and measurement to conceptual and methodological innovations in studying the lived experiences of Black people, Sellers' scholarship centers on the lives of Black communities. Sellers' mentorship and contributions to the professional development of scholars and professionals of color have supported and catalyzed new intergenerational knowledge building by these scholars, ensuring a perpetuating and far-reaching legacy in psychology. In this article, we: (a) celebrate Sellers' enduring contribution to the racial identity literature and its profound impact on psychology as a discipline as well as numerous subfields of psychology, (b) outline his contributions to the racial socialization literature, (c) describe methodological innovations in racial identity and racial socialization research advanced through his scholarship, and (d) summarize his contributions in professional development and mentorship and his leadership roles. Sellers' scholarly contributions and mentorship have transformed the discipline of psychology and the social sciences broadly speaking, making him one of the most influential psychologists in the modern era. (PsycInfo Database Record (c) 2023 APA, all rights reserved).