Labour power (in German: Arbeitskraft; in French: force de travail) is a key concept used by Karl Marx in his critique of capitalist political economy. Marx distinguished between the capacity to do work, labour power, from the physical act of working, labour. Labour power exists in any kind of society, but on what terms it is traded or combined with means of production to produce goods and services has historically varied greatly.

Under capitalism, according to Marx, the productive powers of labour appear as the creative power of capital. Indeed, "labour power at work" becomes a component of capital, it functions as working capital. Work becomes just work, workers become an abstract labour force, and the control over work becomes mainly a management prerogative.