Wage slavery is a term used to criticize exploitation of labour by business, by keeping wages low or stagnant in order to maximize profits. The situation of wage slavery can be loosely defined as a person's dependence on wages (or a salary) for their livelihood, especially when wages are low, treatment and conditions are poor, and there are few chances of upward mobility.

The term is often used by critics of wage-based employment to criticize the exploitation of labor and social stratification, with the former seen primarily as unequal bargaining power between labor and capital, particularly when workers are paid comparatively low wages, such as in sweatshops, and the latter is described as a lack of workers' self-management, fulfilling job choices and leisure in an economy. The criticism of social stratification covers a wider range of employment choices bound by the pressures of a hierarchical society to perform otherwise unfulfilling work that deprives humans of their "species character" not only under threat of extreme poverty and starvation, but also of social stigma and status diminution. Historically, many socialist organisations and activists have espoused workers' self-management or worker cooperatives as possible alternatives to wage labor.

Similarities between wage labor and slavery were noted as early as Cicero in Ancient Rome, such as in De Officiis. With the advent of the Industrial Revolution, thinkers such as Pierre-Joseph Proudhon and Karl Marx elaborated the comparison between wage labor and slavery, and engaged in critique of work while Luddites emphasized the dehumanization brought about by machines. The introduction of wage labor in 18th-century Britain was met with resistance, giving rise to the principles of syndicalism and anarchism.

Before the American Civil War, Southern defenders of keeping African Americans in slavery invoked the concept of wage slavery to favourably compare the condition of their slaves to workers in the North. The United States abolished most forms of slavery after the Civil War, but labor union activists found the metaphor useful – according to historian Lawrence Glickman, in the 1870s through the 1890s "[r]eferences abounded in the labor press, and it is hard to find a speech by a labor leader without the phrase".

The view that working for wages is akin to slavery dates back to the ancient world. In ancient Rome, Cicero wrote that "the very wage [wage labourers] receive is a pledge of their slavery".

In 1763, the French journalist Simon Linguet published an influential description of wage slavery:

The slave was precious to his master because of the money he had cost him ... They were worth at least as much as they could be sold for in the market ... It is the impossibility of living by any other means that compels our farm labourers to till the soil whose fruits they will not eat and our masons to construct buildings in which they will not live ... It is want that compels them to go down on their knees to the rich man in order to get from him permission to enrich him ... what effective gain [has] the suppression of slavery brought [him ?] He is free, you say. Ah! That is his misfortune ... These men ... [have] the most terrible, the most imperious of masters, that is, need. ... They must therefore find someone to hire them, or die of hunger. Is that to be free?

The view that wage work has substantial similarities with chattel slavery was actively put forward in the late 18th and 19th centuries by defenders of chattel slavery (most notably in the Southern states of the United States) and by opponents of capitalism (who were also critics of chattel slavery). Some defenders of slavery, mainly from the Southern slave states, argued that Northern workers were "free but in name – the slaves of endless toil" and that their slaves were better off. This contention has been partly corroborated by some modern studies that indicate slaves' material conditions in the 19th century were "better than what was typically available to free urban laborers at the time". In this period, Henry David Thoreau wrote that "[i]t is hard to have a Southern overseer; it is worse to have a Northern one; but worst of all when you are the slave-driver of yourself."