This set of five volumes offers scholars and students a selection of historical source materials thematically arranged and edited to provide a comprehensive overview of key phenomena and developments pertaining to animals and human-animal relations in (long-)nineteenth-century society. The project adopts a transatlantic framework that brings into dialogue British and American perspectives on relevant subjects from the long nineteenth century, including theological, scientific, and other definitions of human-animal difference; the constitutive role of animality in discourses of race, gender, and sexuality; the emergence of evolutionary theory; early debates about animal welfare and animal rights; and human-animal relations in the contexts of pet culture, work, hunting, and empire, among others. In addition to the broad variety of monographs and manuscript sources, the proliferation of general interest, scientific, and other magazines throughout the long nineteenth century offers critical insights into how these and related topics were debated in Anglophone print culture and contributed to the shaping of British and American society more broadly. The project includes a variety of nonwhite and other marginalized voices on the various topics addressed in the collection, reflecting a broad and inclusive approach to the (hi)storying of human-animal relations. The general introduction and the introductions to the individual volumes/sections bring the collected source materials into conversation with current research in historical and interdisciplinary animal studies and the environmental humanities more broadly.