Social identification denotes individuals’ psychological bond with their ingroup. It is an indispensable construct in research on intragroup and intergroup dynamics. Today’s understanding of social identification is firmly grounded in self-stereotyping principles (i.e., assimilation to the ingroup prototype). However, we argue for a more integrative approach to understand social identification, including a more prominent role for the personal self. We present the Integrative Model of Social Identification (IMSI) and postulate that there are two cognitive pathways to self–group overlap that can simultaneously yet distinctly explain social identification: self-stereotyping and self-anchoring (i.e., projection of personal self onto ingroup). We review different theoretical and methodological approaches to both processes and integrate them into one model. Subsequently, we empirically demonstrate the positive relationship between self-stereotyping, self-anchoring, and identification in various group contexts and individuals. In sum, our model highlights the dynamic interplay of personal and social self as cornerstones of social identification.