This chapter reviews major themes in the history of Western Christianity from the onset of the Western Schism (1378) to the opening of the Council of Trent (1345). Topics include late medieval reform movements, trends in lay religious belief and activity, the papacy and conciliarism, the dominant schools of philosophical and theological thought, heresy and orthodoxy, Renaissance humanism, the early Protestant Reformation and contemporaneous Catholic renewal, and the relationship between Church and state. The scope of the chapter encompasses developments within Western Christianity as well as in its relationship to Eastern Christianity, Judaism, and Islam, as well as its expansion into Asia, Africa, and the Americas. The chapter also considers the effects of general historiographical developments over the last century on church history, such as overarching trends within intellectual and institutional history on the one hand and social and cultural history on the other.