Petty was born in Romsey, where his father and grandfather were clothiers. He was a precocious and intelligent youth and in 1637 became a cabin boy, but was set ashore in Normandy after breaking his leg on board. After this

Petty was knighted in 1661 by Charles II and returned to Ireland in 1666, where he remained for most of the next twenty years.

Petty gained possession of the three baronies of Iveragh, Glanarought and Dunkerron in County Kerry. He soon became a projector, developing extensive plans for an

William Petty married Elizabeth Waller in 1667. She was a daughter of the regicide Sir Hardress Waller (whose life was spared after the Restoration) and

By 1651, Petty was an anatomy instructor at Brasenose College, Oxford, as deputy to Thomas Clayton the younger. He was one of the physicians involved

Despite his political allegiances, Petty was well-treated at the Restoration in 1660, although he lost some of his Irish lands. Charles II at their first meeting brushed aside Petty's apologies for his past support for Cromwell, "seeming to regard them as needless", and

Petty was a friend of Samuel Pepys. He became a founding member of the Royal Society.
Petty is best known for his economic history and statistical writings, before Adam Smith. Of particular interest were his forays into