The British and American Congo Reform Associations were part of a transnational humanitarian movement that sought to end King Leopold II's hold on the Congo Free State. This thesis is a history of that activism and its subsequent impact on British and American foreign policy towards the Congo issue. It provides a sceptical assessment of the impact of the reform agitation on British and American foreign policy regarding the Congo issue by offering a comparative analysis of the efforts of both organisations in lobbying for reform. The Congo activists used transnational networks to pressurise their respective governments into raising the issue to an international level. This study will examine how transatlantic activism concerning Leopold's actions in the Congo Free State developed into a collaborative effort, whilst also analysing the divisions and fractures within the movement, as well as the difficulties of maintaining transatlantic co-ordination at the turn of the twentieth century. Scrutiny of the role of business interests involved in both supporting and opposing the Congo Reform Association (CRA) and American Congo Reform Association (ACRA) permits an assessment of the motives, and influence exerted, of the business figures involved in the CRA specifically, as well as those interests acting against the wider movement. Congo apologists often claimed that the Congo reform movement was driven by the commercial ambitions of Liverpool shipping merchants, whereas the motives of the activists campaigning for reform are often perceived to be purely altruistic in nature. This thesis argues that quite the opposite was often true of certain members who were self-interested in relation to their drives and ambitions in campaigning for reform in the Congo and used the movement to deflect attention from their own suspect business practices, or attack rivals in the shipping industry. Furthermore, this study offers an assessment of where the British and American associations sit within the history of humanitarian and human rights organisations, positing that they were a bridge between the antislavery movements of the late eighteenth and nineteenth centuries. Overall, this thesis offers a detailed examination of the successes and limitations of the transnational activism of both associations during the period of Congo reform activism at the beginning of the twentieth century.