Carl Menger von Wolfensgrün (/ˈmɛŋɡər/; German: [ˈmɛŋɐ]; 28 February 1840 – 26 February 1921) was an Austrian economist who contributed to the marginal theory of value. Menger is considered the founder of the Austrian school of economics.

In building his marginalist approach, Menger rejected many established views of classical economics. He directly disputed the view of the "German school" that economic theory could be derived from history. Departing from the cost-of-production theory of value—the prevailing theory of Adam Smith, David Ricardo, and Karl Marx—Menger's subjective theory of value emphasized role of mutual agreement in deriving prices. Although he had few readers outside Vienna until late in his career, disciples including Eugen von Böhm-Bawerk and Friedrich von Wieser brought his theories into wider readership. Friedrich Hayek wrote that the Austrian school's "fundamental ideas belong fully and wholly to Carl Menger."

Menger began his career as a lawyer and business journalist, during which he saw inconsistencies between existing economic theory and how buyers reasoned. After formal training in economics, he taught at the University of Vienna from 1872 to 1903. He became a private tutor and confidant to Rudolf von Habsburg, the crown prince of Austria.

Carl Menger von Wolfensgrün was born in the city of Neu-Sandez in the Kingdom of Galicia and Lodomeria, Austrian Empire, which is now Nowy Sącz in Poland. He was the son of a wealthy family of minor nobility; his father, Anton Menger, was a lawyer. His mother, Caroline Gerżabek, was the daughter of a wealthy Bohemian merchant. He had two brothers, Anton and Max, both prominent as lawyers. His son, Karl Menger, was a mathematician who taught for many years at Illinois Institute of Technology.

After attending Gymnasium, he studied law at the universities of Prague and Vienna and later received a doctorate in jurisprudence from the Jagiellonian University in Kraków. In the 1860s Menger left school and enjoyed a stint as a journalist reporting and analyzing market news, first at the Lemberger Zeitung in Lemberg, Austrian Galicia (now Lviv, Ukraine) and later at the Wiener Zeitung in Vienna.^{[citation needed]}

During the course of his newspaper work, he noticed a discrepancy between what the classical economics he was taught in school said about price determination and what real world market participants believed. In 1867, Menger began a study of political economy which culminated in 1871 with the publication of his Principles of Economics (Grundsätze der Volkswirtschaftslehre), thus becoming the father of the Austrian school of economics. It was in this work that he challenged classical cost-based theories of value with his theory of marginality – that price is determined at the margin.

In 1872 Menger was enrolled into the law faculty at the University of Vienna and spent the next several years teaching finance and political economy both in seminars and lectures to a growing number of students. In 1873, he received the university's chair of economic theory at the very young age of 33.

In 1876 Menger began tutoring Archduke Rudolf von Habsburg, the crown prince of Austria, in political economy and statistics. For two years, Menger accompanied the prince during his travels, first through continental Europe and then later through the British Isles. He is also thought to have assisted the crown prince in the composition of a pamphlet, published anonymously in 1878, which was highly critical of the higher Austrian aristocracy. His association with the prince would last until Rudolf's suicide in 1889.