Personality and social relationships influence each other in multiple and consequential ways. To understand how people differ from each other in their personality and social behavior, how these differences develop, and how this affects further life outcomes, we need to better understand the interplay of personality and social relationships. Here, we provide an integrative overview on personality-relationship research across relationship types (everyday encounters, friendships, romantic, and family relationships), and personality characteristics. We summarize the state of research on (a) how much relationship aspects vary across actors, partners, and actor-partner relations, (b) which personality characteristics predict these variance components (i.e. actor, partner, and relationship effects), and (c) how social relationships work as contexts for personality development. Following an integrative process framework, key open questions are discussed concerning the processes that underlie personality-relationship and relationship-personality effects. We conclude with a call for conceptual integration, methodological expansion, and collaborative action.