The Ottoman Empire’s territorial and maritime reach throughout its nearly 600-year existence is nothing short of extraordinary. Considering the plethora of adversaries at whose expense the empire continued to expand, its boundaries and their movement over time deserve close attention as sites of cultural, socioeconomic, as well as political history. Here we explore the theme of Ottoman borders as critical windows into the dynamics shaping the larger empire, including the great urban centers often located far from these frontiers. In providing a summary of the territorial limits (or beginnings) of this multiethnic empire, we provide insights into the complexities that constitute the processes by which the Ottomans administered as much as lived in these regions. Be they witness to the stability that accompanied peace between neighboring states or the frequent volatility caused by war, the empire’s edges served as theaters for intraimperial development that shaped subject and state alike.