Mercantilism is a form of economic system and nationalist economic policy that is designed to maximize the exports and minimize the imports of an economy. It seeks to maximize the accumulation of resources within the country and use those resources for one-sided trade.

The concept aims to reduce a possible current account deficit or reach a current account surplus, and it includes measures aimed at accumulating monetary reserves by a positive balance of trade, especially of finished goods. Historically, such policies may have contributed to war and motivated colonial expansion. Mercantilist theory varies in sophistication from one writer to another and has evolved over time.

Mercantilism promotes government regulation of a nation's economy for the purpose of augmenting and bolstering state power at the expense of rival national powers. High tariffs, especially on manufactured goods, were almost universally a feature of mercantilist policy. Before it fell into decline, mercantilism was dominant in modernized parts of Europe and some areas in Africa from the 16th to the 19th centuries, a period of proto-industrialization. Some commentators argue that it is still practised in the economies of industrializing countries in the form of economic interventionism.

With the efforts of supranational organizations such as the World Trade Organization to reduce tariffs globally, non-tariff barriers to trade have assumed a greater importance in neomercantilism.

Mercantilism became the dominant school of economic thought in Europe throughout the late Renaissance and the early modern period (from the 15th to the 18th centuries) before advent of Classical liberalism. Evidence of mercantilistic practices appeared in early modern Venice, Genoa, and Pisa regarding control of the Mediterranean trade in bullion. However, the empiricism of the Renaissance, which first began to quantify large-scale trade accurately, marked the beginning of mercantilism as a codified school of economic theories. The Italian economist and mercantilist Antonio Serra is considered to have written one of the first treatises on political economy in his 1613 work, A Short Treatise on the Wealth and Poverty of Nations.

Mercantilism, in its simplest form, is all about bullionism, or the theory that a nation's wealth is measured in terms of how much precious metal, particularly gold and silver, it possesses. Mercantilist authors were concerned with the movement of money, however, more than with the hoarding of it. They felt that money needed to move through the economy to induce trade and economic activity, a concept different from that of simply amassing wealth. This focus on money's role, specifically precious metals, mirrors modern discussions of the money supply and its implications for economic growth, i.e., how money supply expansion can stimulate economic activity. However, with the advent of fiat money (money not backed by a physical commodity) and floating exchange rates, the importance of specie (gold and silver) in economic systems has diminished. Progressively, the focus shifted from the handling of money to the implementation of industrial policies that placed greater economic goals, e.g., stimulating general prosperity and supporting technological and industrial advancement, above the financing of war.

England began the first large-scale and integrative approach to mercantilism during the Elizabethan Era (1558–1603). An early statement on national balance of trade appeared in Discourse of the Common Wealth of this Realm of England, 1549: "We must always take heed that we buy no more from strangers than we sell them, for so should we impoverish ourselves and enrich them." The period featured various but often disjointed efforts by the court of Queen Elizabeth I (r. 1558–1603) to develop a naval and merchant fleet capable of challenging the Spanish stranglehold on trade and of expanding the growth of bullion at home. Queen Elizabeth promoted trade and navigation acts in Parliament and issued orders to her navy for the protection and promotion of English shipping.^{[citation needed]} The first Navigation Acts regulating trade were passed by Parliament in 1651 and 1652, during the English Commonwealth.

Authors noted most for establishing the English mercantilist system include Gerard de Malynes (fl. 1585–1641) and Thomas Mun (1571–1641), who first articulated the Elizabethan system (England's Treasure by Foreign Trade or the Balance of Foreign Trade is the Rule of Our Treasure), which Josiah Child (c. 1630/31–1699) then developed further.