This article considers British early nineteenth century attempts to reclaim Sagar Island, at the southwestern extremity of the Bengal delta, by clearing the island of jungle and settling and cultivating it—a project led first by colonial authorities at Calcutta and then by a joint-stock company established for the purpose, the Sagar Island Society. It considers the motivations behind the reclamation attempts, what they involved, and why they failed. The consequences – economic, human, and ecological—of the reclamation attempts are examined. The article reconstructs the almost entirely unknown history of events on Sagar Island from 1810 to 1833 through extensive new archival research and the study of rarely consulted publications from the period, before exploring their implications. In doing so, it sheds new light on the nature of British colonial capitalism and the environmental impact of British colonial interventions in South Asia, contributing to our understanding of the economic and environmental history of colonial Bengal and of the wider British imperial world. The article contends that events on Sagar Island offer a cautionary lesson about public and private initiatives to extend the frontiers of revenue extraction, and about the hubris of human efforts to ‘improve’ natural environments through large-scale projects of transformation. New insights are offered into the collusion between government and capital in British Bengal between the East India Company charter acts of 1813 and 1833, and into the colonial and capitalist origins of the Anthropocene.