Researchers have documented capitalism’s pernicious effects on the health of the poor and working class since the beginning of the industrial revolution. In this chapter, we summarize and critically assess the relationship between capitalism and mental health. We begin by defining capitalism - broadly, a socio-economic system characterized by the private ownership of the means of production and the exploitation and domination of wage labor for profit. We then review early research on capitalism and mental health, focusing on Engels’s and Marx’s work, which described how 19th-century capitalist industrialization damaged workers’ mental health by degrading their social, working, and living conditions. Next, we jump ahead to quantitative research on capitalism and mental health since the mid-20th century. Although epidemiologic research on the topic remains underdeveloped, research consistently finds that capitalism harms workers’ mental health and exacerbates inequities. It does so through at least three mechanisms - 1) Alienation, capitalism separates workers from control over the processes and products of their labor; 2) Exploitation, under capitalism, capitalists compensate workers less than the value of workers’ production; and 3) Domination, under capitalism, capitalists control workers’ labor processes through hierarchy, surveillance, and sanctions. Finally, we argue that the mental health effects of other axes of power, like racism, sexism, colonialism, and imperialism, cannot be fully understood without attending to their historically contingent forms under capitalism; likewise, capitalism’s mental health effects cannot be understood without attending to these other axes of power.