A plague pit is the informal term used to refer to mass graves in which victims of the Black Death were buried. The term is most often used to describe pits located in Great Britain, but can be applied to any place where bubonic plague victims were buried.
The plague which swept across Europe in the 14th century is estimated to have killed between one-third and two-thirds of Europe's population. Disposal of the bodies of those who died presented huge problems for the authorities, and eventually the normal patterns of burial and funerary observance broke down.
Plague pits were used especially often during major plague outbreaks, such as the London epidemic of 1665. During these times, graveyards rapidly filled, and such graves became available only to wealthy people. Parishes became strained; one example, the records of St Bride's Church on Fleet Street during the London 1665 plague, shows typical methods employed by the parishes.
In 1665, the total number of deaths in the parish rose to five and a half times their normal number, with 2,111 deaths overall and 1,427 attributed to plague.
Some scientists have put forward the idea that the Black Death was not caused by Yersinia pestis as some have thought, and some evidence of this has been found in plague pits, where the pathogens of other diseases, such as anthrax, have been discovered.