The introductory chapter presents the thematic, geographical, and chronological scope of the volume and explicates its guiding questions and conceptual framework. Our focus is on the Baltic Sea region, considered as a multi-layered space of intercultural encounter and conflict and its specific legacy of hospitality. In terms of guiding concepts for the empirical chapters, this introduction combines issues of host–guest relations with the problems of securitization. It is our contention that hospitality in Baltic migration contexts, from the turn of the first millennium until the twentieth century and beyond, triggered security issues both on the part of arriving strangers and receiving host communities. Why and how were multifarious categories of guests and strangers—migrants, war refugees, prisoners of war, merchants, missionaries, vagrants, vagabonds, etc.—portrayed as threats to local populations or as objects of their charity? Under what circumstances did hospitality turn into hostility? How was hospitality practiced and contained spatially? By focusing predominantly on coastal contexts as spaces for meetings and confrontations, we decouple the study of hospitality and migration from state-centered methodology. Instead, we offer a close-up view on hospitality dilemmas and practices of dealing with arriving guests and strangers, which we consider in transhistorical perspective. These conceptual themes and problems are fleshed out in the presentation of the individual chapters.