The Black Death, also known as the Pestilence (Pest for short), the Great Plague or the Plague, or less commonly the Black Plague, was one of the most devastating pandemics in human history, resulting in the deaths of an estimated 75 to 200 million people in Eurasia, peaking in Europe from 1347 to 1351. The bacterium Yersinia pestis, which results in several forms of plague(septicemic, pneumonic and, the most common, bubonic) is believed to have been the cause. The Black Death was the first major European outbreak of plague and the second plague pandemic. The plague created a number of religious, social and economic upheavals, with profound effects on the course of European history.

The Black Death is thought to have originated in the dry plains of Central Asia or East Asia, where it travelled along the Silk Road, reaching Crimea by 1343. From there, it was most likely carried by fleas living on the black rats that traveled on all merchant ships, spreading throughout the Mediterranean Basin and Europe.

The Black Death is estimated to have killed 30% to 60% of Europe's population. In total, the plague may have reduced the world population from an estimated 475 million to 350?375 million in the 14th century. It took 200 years for Europe’s population to recover to its previous level and some regions like Florence only recovered by the 19th century. The plague recurred as outbreaks until the early 20th century.