Sir William Petty (1623-1687) was a scientist and philosopher. Born as the son of a Hampshire clothier, Petty held extensive holdings in Ireland due to association with Oliver Cromwell and Commonwealth. He was Member of Parliament briefly, being a scientist, inventor, and entrepreneur, and was a charter member of the Royal Society. Knighted in 1661. He was the great-grandfather of William Petty Fitzmaurice.
He is most well known for economic history and statistic writings, pre-Adam Smith.