Mercantilism is an economic theory that the prosperity of a nation depends upon its supply of capital, and that the global volume of trade is "unchangeable." Economic assets, or capital, are represented by bullion (gold, silver, and trade value) held by the state, which is best increased through a positive balance of trade with other nations (exports minus imports). Mercantilism suggests that the ruling government should advance these goals by playing a protectionist role in the economy, by encouraging exports and discouraging imports, especially through the use of tariffs. The economic policy based upon these ideas is often called the mercantile system.

Though traces of merchant capitalism can be found in the Roman Empire, mercantilism was established during the early modern period (starting in the 16th to the 18th century, which roughly corresponded to the emergence of the nation-state). This led to some of the first instances of significant government intervention and control over market economies, and it was during this period that much of the modern capitalist system was established. Internationally, mercantilism encouraged the many European wars of the period, and fueled European imperialism, as the European powers fought over "available" markets. Belief in mercantilism began to fade in the late 18th century, as the arguments of Adam Smith and the other classical economists won favour in the British Empire (among such advocates as Richard Cobden) and to a lesser degree in the rest of Europe (with the notable exception of Germany where the Historical school of economics was favored throughout the 19th and early 20th century). Some have said that America chose not to adhere to classical economics, preferring a form of neo-mercantilism embodied by the "American School," but in 1792 Alexander Hamilton, basing his policies on his study of Adam Smith, established a gold standard designed to conform to that of Britain to promote international trade. America drifted from the gold standard a number of times prior to the Great Depression, but always returned to the Hamilton gold standard. The Great Depression influenced American government to return to neo-mercantilism imposing high protectionist tariffs and suspending private ownership of gold. Finally, during the New Deal, the currency was devalued based on the government’s new neo-mercantilist leaning. Today, mercantilism has seen a resurgence in economic theories that focus on the trade surplus and deficit as determinants of monetary value, but mercantilism as a whole is rejected by many economists. However, elements of mercantilism are still accepted by some economists including Ravi Batra, Pat Choate, Eammon Fingleton, and Michael Lind.