AbstractThe Free Port Act of 1766 was an important reform in British political economy during the so-called imperial crisis between the Seven Years’ War (1756–1763) and the American Revolution (1775–1783). In an explicit break from the letter if not the spirit of the Navigation Acts, the act opened six British ports in the West Indies (two in Dominica and four in Jamaica) to foreign merchants trading in a highly regulated number of goods subject to various duties. Largely understudied, this legislation has been characterized in most previous work on the subject as a fundamental break from British mercantile policies and meant to benefit North American colonial merchants. This article proposes a different interpretation. Based on the wider context of other imperial free port models, the loss of conquests such as French Guadeloupe and Martinique and Spanish Havana in the 1763 Paris Peace Treaty, a postwar downturn in Anglo-Spanish trade, and convincing testimonies by merchants and colonial observers, policy makers in London conceived of free ports primarily as a means of extending Britain's commercial empire. The free port system was designed to ruin the rival Dutch trade economically and shackle Spanish and French colonists to Britain's mercantile, manufacturing, and slaving economies. The reform marks a key moment in the evolution of British free trade imperial designs that became prevalent in the nineteenth century and beyond.