John Graunt (24 April 1620 – 18 April 1674) was one of the first demographers, though by profession he was a haberdasher. Born in London, the eldest of seven or eight children of Henry and Mary Graunt. His father was a draper who had moved to London from Hampshire. In February 1641, Graunt married Mary Scott, with whom he had one son (Henry) and three daughters.

Graunt, along with William Petty, developed early human statistical and census methods that later provided a framework for modern demography. He is credited with producing the first life table, giving probabilities of survival to each age. Graunt is also considered as one of the first experts in epidemiology, since his famous book was concerned mostly with public health statistics.

His book Natural and Political Observations Made upon the Bills of Mortality (1662 Old Style or 1663 New Style) used analysis of the mortality rolls in early modern London as Charles II and other officials attempted to create a system to warn of the onset and spread of bubonic plague in the city. Though the system was never truly created, Graunt's work in studying the rolls resulted in the first statistically based estimation of the population of London.