An Inquiry into the Nature and Causes of the Wealth of Nations, (generally referred to by its shortened title The Wealth of Nations), is the magnum opus of the Scottish economist and moral philosopher Adam Smith. First published in 1776, the book offers one of the world's first collected descriptions of what builds nations' wealth and is today a fundamental work in classical economics. Through reflection over the economics at the beginning of the Industrial Revolution the book touches upon broad topics as the division of labour, productivity and free markets. It influenced a number of authors and economists, as well as governments and organizations. For example, Alexander Hamilton was influenced in part by The Wealth of Nations to write his Report on Manufactures, in which he argued against many of Smith's policies. Interestingly, Hamilton based much of this report on the ideas of Jean-Baptiste Colbert, and it was, in part, Colbert's ideas that Smith responded to with The Wealth of Nations.

Many other authors were influenced by the book and used it as a starting point in their own work, including Jean-Baptiste Say, David Ricardo, Thomas Malthus and, later, Ludwig von Mises. The Russian national poet Aleksandr Pushkin refers to The Wealth of Nations in his 1833 verse-novel Eugene Onegin.

Irrespective of historical influence, The Wealth of Nations represented a clear shift in the field of economics, similar to Sir Isaac Newton's Principia Mathematica for physics, Antoine Lavoisier's Traité Élémentaire de Chimie for chemistry, or Charles Darwin's On the Origin of Species for biology.