Rome was not the first state to use coinage, but it was the first to use it at the scale of an empire. The denarius — the standard silver coin of the Republic and early Empire — circulated from Britain to Mesopotamia, funding armies, paying officials, and enabling the commercial transactions that integrated the Mediterranean economy. The story of Roman coinage is in some sense the story of Roman fiscal history: how the empire monetized its power, how it debased its currency under fiscal pressure, and how the collapse of monetary confidence contributed to the political and economic crisis of the third century.