Many everyday conversations, whether between close partners or strangers interacting for the first time, are about the world external to their relationship, such as music, food, or current events. Yet, the focus of most research on interpersonal relationships to date has been on the ways in which partners perceive each other and their relationship. We propose that one critical aspect of interpersonal interactions is developing a sense of dyadic, generalized shared reality-the subjective experience of sharing a set of inner states (e.g., thoughts, feelings, or beliefs) in common with a particular interaction partner about the world in general, including the world external to the relationship. Across 9 studies, we use mixed methods to investigate the unique role of generalized shared reality in interpersonal interactions, both between close partners and strangers. We hypothesize that generalized shared reality predicts how people connect with each other and perceive the world around them. We also investigate the observable, dyadic behavioral signatures of generalized shared reality in interpersonal interactions. Finally, we examine the motivation to uphold an existing sense of generalized shared reality. We hypothesize that couples high on baseline generalized shared reality exhibit motivated, dyadic interaction behaviors to reaffirm their generalized shared reality in the face of experimentally manipulated threat. By identifying a unique dimension of everyday interactions, these studies aim to capture a critical aspect of the lived subjective experience of human relationships that has not been captured before. (PsycInfo Database Record (c) 2020 APA, all rights reserved).