The scholarship on borderlands has burgeoned over the last quarter century, broadening the concept and extending its historical and geographical reach to a wide range of latitudes throughout the Americas. In addition, innovative research has taken the field of borderlands studies into maritime and fluvial environments to encompass networks of exchange that developed throughout the Caribbean and traversed both the Atlantic and Pacific oceans, linking the Americas to Europe, Asia and Africa. This panel, subtitled “Iberian Borderlands in the Americas and Beyond,” emphasizes the global reach of Spanish and Portuguese imperial spheres and the historical agency of the myriad peoples who shaped the borderlands through parallel processes of mobility, settlement, labor, and war. Imperial boundaries mattered in the early modern world, but borderlands emerged often as different clusters of people transcended those boundaries through both forced and free migrations, travel, and trade that passed through different territorial dominions. The four presenters in this panel explore these issues in widely different geographical and historical regions. Fabrício Prado explores the Atlantic world borderland in the Río de la Plata, the great riverway long disputed by diverse indigenous nations, Spanish, and Portuguese, which became an area intervened by Dutch and British merchants, slave traders, and smugglers. Barbara Sommer turns to the “vast inland sea” of the Amazon basin to discuss the role of interethnic alliances and marriages in changing identities and in the weaving of complex and conflicting relations among indigenous groups, Portuguese, and mixed-race peoples through patterns of mobility that followed the geographical webs of riverine tributaries leading from the northwest to the Atlantic. José Manuel Moreno develops the theme of interethnic borderlands through the ritualized practices of reciprocal gift-giving, focusing on three Native American groups – Chiricahua Apache, Northern Pima, and Seri – and Spanish military and missionary authorities on the edges of colonial governance in the colonial setting of northern New Spain (Northwestern Mexico). Danna Levin Rojo brings to light the territorial disputes in New Mexico, under Mexican national rule, between the Hispanic vecinos of Bernalillo and the Pueblo of Sandía. Her analysis of the protracted legal case (1829-1841) addresses the challenges frontier peoples faced in the context of changing sovereignties and geopolitical transitions. These four papers present original research that demonstrates the widely divergent historical actors who shaped inter-imperial and interethnic borderlands in both North and South America.