The self-expansion model posits that individuals are motivated to broaden their sense of self by acquiring new identities, developing new perspectives, enhancing capabilities, and gaining resources. The self-expansion motivation is driven by individuals' desire to increase their potential self-efficacy and ability to accomplish goals. In this article, we discuss two main ways individuals self-expand – by forming relationships and including the other in the self and through engaging in novel activities that are challenging and/or interesting either on one's own or with a relationship partner. We provide an overview of recent research detailing the numerous interpersonal and intrapersonal benefits and implications of self-expansion. Additionally, we differentiate self-expansion from a series of potentially associated constructs.