This chapter examines the urban evolution of Trier in Late Antiquity, focusing on its transformation from a Roman provincial centre to an imperial capital. It discusses the city’s development from its foundation as Augusta Treverorum in the first century BCE to its peak as a key administrative and military hub in the late third and fourth centuries. This contribution integrates archaeological evidence, historical texts and urban-planning analysis, highlighting how Trier’s strategic location along the Moselle River contributed to its economic and political rise. The chapter also considers major infrastructure projects, including the construction of city walls, bridges, baths, an amphitheatre and a palace complex, demonstrating how imperial patronage shaped the city’s expansion. A significant theme is Trier’s role as an imperial residence under Constantine and his successors, with the city becoming a centre for coin production, governance and military strategy. The Christianisation of Trier is another focus, detailing the construction of basilicas, episcopal complexes and martyr shrines, which established it as an important religious centre. Despite political upheavals and invasions, Trier remained influential into the early medieval period, with the chapter concluding that its evolution reflects broader patterns of imperial consolidation, economic resilience and religious transformation in Late Antiquity.