This chapter explores the spread of Christianity in Late Antiquity, focusing on archaeological evidence and methodological challenges in tracing its expansion. It examines how Christianity transitioned from a marginalised faith to an institutionalised religion, emphasising regional differences in its adoption across the Mediterranean and beyond. The chapter discusses a variety of materials, including early Christian inscriptions, artefacts, funerary practices and architectural remains such as churches, baptisteries and monasteries. Sites like the house church at Dura Europos and early Christian catacombs provide crucial insights into the religion’s early development. The study also highlights the role of missionary activity and the influence of state policies, particularly after Constantine’s legalisation of Christianity in the fourth century. A major argument is that Christianity spread unevenly, with urban centres adopting it earlier than rural areas. The transition was not uniform, as some regions experienced periods of resistance or syncretism with existing religious traditions. The chapter underscores the difficulty of identifying Christian material culture due to the overlap with pagan symbols. The chapter rounds off by calling for a more critical approach to interpreting archaeological evidence and suggests that future research should focus on regional case studies to refine our understanding of Christianity’s complex expansion.