Soy has become one of the world's most important agroindustrial commodities – serving as the nexus for the production of food, animal feed, fuel and hundreds of industrial products – and South America has become its leading production region. The soy boom on this continent entangles transnational capital and commodity flows with social relations deeply embedded in contested ecologies. In this introduction to the collection, we first describe the 'neo-nature' of the soy complex and the political economy of the sector in South America, including the new corporate actors and financial mechanisms that produced some of the world's largest agricultural production companies. We then discuss key environmental debates surrounding soy agribusiness in South America, challenging especially the common arguments that agroindustrial intensification 'spares land' for conservation while increasing production to 'feed the world'. We demonstrate that these arguments hinge on limited data from a peculiar portion of the southern Amazon fringe, and obfuscate through neo-Malthusian concerns multiple other political and ecological problems associated with the sector. Thus, discussions of soy production become intertwined with broader debates about agrarian development, industrialization and modernization. Finally, we briefly outline the contributions in this volume, and identify limitations and fruitful directions for further research.