This book is a critical history of the concept of environment from the late eighteenth century to the present. Situating key episodes of that history in their material, social, cultural, and political contexts, it makes an argument for environmental pluralism—that is, for recognizing the profound variations in the way the concept of environment has been defined and put into practice in different times and places. Adopting this pluralistic perspective, the book argues, has several benefits. First, it provides both a more accurate and a more capacious account of the history of this multifarious concept than any attempt to identify a single dominant tradition or overarching trajectory could do. Second, it helps us recognize the diversity of concepts of environment and forms of environmentalism that are emerging at the present time, many of which diverge from those associated with the modern environmental movement. The episodes discussed in the book include research at the Paris Museum of Natural History following its founding in 1793, imperial medicine in the British Caribbean, urban reform in Progressive Era Chicago, resource management and ecology from World War I to the early Cold War, consumer protection and the environmental movement in the postwar United States, and climate change science and activism since the 1970s. The book concludes by describing several promising forms of environmentalism that are emerging today, each of which defines the concept of environment and puts it into practice in its own distinctive way.