The Plague of Justinian was a pandemic that afflicted the Byzantine Empire, including its capital Constantinople, in the years 541–542 AD. The most commonly accepted cause of the pandemic is bubonic plague, which later became infamous for either causing or contributing to the Black Death of the 14th century. Its social and cultural impact is comparable to that of the Black Death.
In the views of 6th century Western historians, it was nearly worldwide in scope, striking central and south Asia, North Africa and Arabia, and Europe as far north as Denmark and as far west as Ireland. The plague would return with each generation throughout the Mediterranean basin until about 750.
The plague would also have a major impact on the future course of European history. Modern historians named it after the Eastern Roman Emperor Justinian I, who was in power at the time and himself contracted the disease. Modern scholars believe that the plague killed up to 5,000 people per day in Constantinople at the peak of the pandemic. It ultimately killed perhaps 40 percent of the city’s inhabitants. The initial plague went on to destroy up to a quarter of the human population of the eastern Mediterranean.