The Black Death of 1347–1353 was the worst demographic catastrophe in recorded history, killing perhaps a third of Europe's population, but its origins lie in the ancient and medieval disease ecology of Central Asia where the plague bacterium Yersinia pestis maintained itself in rodent reservoir populations for centuries.

The plague reached Europe via the Black Sea trade routes from Central Asia, carried by rats on merchant ships. The Italian city-states, with their dense populations and active Mediterranean trade networks, were hit first and most severely. Florence, a city of perhaps 100,000 before the plague, lost half its population within a year; many smaller Italian towns lost even higher proportions.

The social and cultural responses documented by contemporary sources reveal the extremity of the crisis. Boccaccio's Decameron, framed as stories told by young Florentines who have fled the city for a country villa, describes the breakdown of social bonds — the abandonment of the sick by their families, the mass burials, the suspension of normal civic and religious life — alongside the resilience that produced the storytelling frame.

The plague's demographic impact shaped European history for a century: labor shortages shifted bargaining power toward surviving peasants, contributing to the end of serfdom in western Europe; intellectual responses to mass death contributed to both the flagellant movement and a new attention to the body, individual mortality, and medical knowledge that some scholars see as preparation for the Renaissance.