This dissertation examines how material interactions between slaveholders, enslaved people, and nonhuman animals shaped the territorial expansion of the British Empire in the era of the Atlantic slave trade. My project is an environmental history of slavery and slaving from the Royal African Company's entrance into the castle trade in 1672 through the American Revolution to the abolition of the trade in 1808. I argue that human-animal entanglements generated by slaving constituted a decisive factor in expanding the political, scientific, and economic networks of the empire. Inhuman Empire challenges the predominantly European frame fo ecological imperialism by interrogating the ecological, social, and cultural interplay between English enslavers, Atlantic Africans, and animals. I use the theoretical frameworks of eco-cultural networks and modes of interaction to draw out how these relations shaped the expanding geography of slavery in the British Atlantic world. English and African traders exchanged animals as propitiatory sacrifices, gifts, and media of exchange to forge bonds of alliance and commerce on the Gold Cost and the Bight of Benin. Naturalists studying the faunal environments of slave depots from New Spain to North American plantations became slaveholders or relied on the judgement and collecting efforts of enslaved people to gather specimens for natural history collections. On Caribbean and Chesapeake plantations, enslavers raising sugar and tobacco harnessed the labor and bodily energy of slaves and draft animals. However, many animals proved difficult to control in the pursuit of imperial profits. Intractable vermin ruined plantations at alarming rates, and planters produced the category of pests to describe the animals beyond their control. Most importantly, enslaved people resisted their bondage and undermined the institution of slavery by injuring, starving, or stealing animals for their own purposes, while black intellectuals produced critiques of slavery as the foundation of an 'inhuman" empire as central to the campaign to abolish the slave trade. The centrality of human-animal networks that supported slaving and slavery is one conclusion of this dissertations, which intervenes in early American environmental history. A second conclusion is that this environmental history provides a valuable materialist account that supports formerly enslaved people's narratives and experiences of becoming less-than-fully human animalized subjects in the long eighteenth century.