Like many nineteenth-century sciences, phrenology had global aspirations. Skulls were collected in Egypt and Ceylon, societies exchanged journals between India and the United States, and phrenological bestsellers were sold in Shanghai and Tokyo. Despite this wealth of interaction, existing accounts treat phrenology within neat national and urban settings. In contrast, this article examines phrenology as a global political project. During an age in which character dominated public discourse, phrenology emerged as a powerful political language. In this article, I examine the role that correspondence played in establishing material connections between phrenologists and their political concerns, ranging from the abolition of slavery to the reform of prison discipline. Two overarching arguments run throughout my case-studies. First, phrenologists used correspondence to establish reform as a global project. Second, phrenology allowed reformers to present their arguments in terms of a new understanding of human character. More broadly, this article connects political thought with the global history of science.