This is a study of Irish-born Richard Cantillon, eighteenth century banker and economist whose Essai sur la Nature du Commerce en General (1755), published twenty-one years after his death, remains a significant contribution to the development of monetary theory. Cantillon's life was an exciting story of involvement in high-level international banking, and speculation in foreign exchanges, commodities and stocks at the time of the South Sea Bubble. His death occurred in mysterious circumstances.