Léon Walras (1834-1910) was one of the key thinkers behind the development of marginal utility theory and his introduction of general equilibrium theory is one of the cornerstones of modern economic thought. Now, for the first time, his seminal work Études d'économie politique appliquée, first published in 1898, is available in English. This work sits aside Éléménts d'économie politiquepure(1874) and Études d'économie sociale(1896) as one of Walras' crowning achievements. Only the former book, in which Walras advocated regulated free competition, has been translated. In Études d'économie politique appliquée, Walras elaborates on his equilibrium theory and established it as a basis for an optimal economic order. This two-volume translation of a text that still holds vibrant relevance for economists today, stands as a milestone in marginal utility theory, and will be of immense interest to working economists and students of the history of economic thought.