The concept of the Amazon River as we know it today emerged in the middle of the seventeenth century, when maps and accounts focused exclusively on the river began to circulate following a series of Iberian expeditions in the late 1630s. Before that, the Amazon already existed, but under dissimilar outlines and names: “Mar Dulce,” “Río Grande,” “Marañón,” “Orellana,” and eventually “Amazon.” Offering the first comprehensive geographic and cartographic history of the early modern Amazon River, Roberto Chauca Tapia traces these multiple hydronyms and forms to reveal the tribulations of Western colonialism in the New World, the Indigenous and European agents who participated in this process, and the contradictory parameters they used to define the river. In the end, A River of Many Names demonstrates that pilots and explorers “discovered” not just one “Amazon” but many “Amazons.”