Borders are known for their paradoxical qualities. Sometimes they are shifting and porous, lines in the sand constituted more by subjective experience than by legal definition; at other times they harden into walls, are heavily securitized, and their primary function becomes keeping the unwanted out. Challenging Borders: Contingencies and Consequences sets out to explore the concrete, complex effects of borders on human aspirations and lives, while at the same time underscoring the diversity of individual encounters with these deceptively invisible lines. Drawing on insights from history, geography, Indigenous studies, political science, refugee and migration studies, the visual arts, and even physics, contributors to the collection examine the role of borders in the ongoing negotiation of national identities, in contested claims of sovereignty and belonging, in the tensions between freedom of movement and restrictions on entry, and in the use of violence in the name of security. As the essays illustrate, in the context of migration, borders are inherently a site of struggle—at once a source of hope for those seeking sanctuary and an excuse for others to deny it. Indigenous nations, migrants, and refugees have long known how destructive colonial boundaries can be, and this volume offers compelling new angles from which to map the geographies of oppression and resistance.