Georgism, in modern times also called Geoism, and known historically as the single tax movement, is an economic ideology holding that people should own the value that they produce themselves, while the economic rent derived from land—including from all natural resources, the commons, and urban locations—should belong equally to all members of society. Developed from the writings of American economist and social reformer Henry George, the Georgist paradigm seeks solutions to social and ecological problems based on principles of land rights and public finance that attempt to integrate economic efficiency with social justice.

Georgism is concerned with the distribution of economic rent caused by land ownership, natural monopolies, pollution rights, and control of the commons, including title of ownership for natural resources and other contrived privileges (e.g., intellectual property). Any natural resource that is inherently limited in supply can generate economic rent, but the classical and most significant example of land monopoly involves the extraction of common ground rent from valuable urban locations. Georgists argue that taxing economic rent is efficient, fair, and equitable. The main Georgist policy recommendation is a tax assessed on land value, arguing that revenues from a land value tax (LVT) can be used to reduce or eliminate existing taxes (such as on income, trade, or purchases) that are unfair and inefficient. Some Georgists also advocate for the return of surplus public revenue to the people by means of a basic income or citizen's dividend.

Henry George popularized the concept of gaining public revenues mainly from land and natural resource privileges with his first book, Progress and Poverty (1879). The philosophical basis of Georgism draws on thinkers such as John Locke, Baruch Spinoza, and Thomas Paine. Economists from Adam Smith and David Ricardo to Milton Friedman and Joseph Stiglitz have observed that a public levy on land value does not cause economic inefficiency, unlike other taxes. A land value tax also has progressive tax effects. Advocates of land value taxes argue that they reduce economic inequality, increase economic efficiency, remove incentives to under-utilize urban land, and reduce property speculation.

Georgist ideas were popular and influential during the late 19th and early 20th centuries. Political parties, institutions, and communities were founded on Georgist principles during that time. Early devotees of George's economic philosophy were often termed Single Taxers for their political goal of raising public revenue mainly or only from a land-value tax, although Georgists endorsed multiple forms of rent capture (e.g. seigniorage) as legitimate. The term Georgism was invented later, and some prefer the term geoism as more generic.