Karl Marx (1818–1883) was a German philosopher, economist and sociologist, as well as a political revolutionary. Capital was one of his most important works, and Marx spent about thirty years writing it. The first volume (which this study guide focuses on exclusively) was published in 1867. It was the only volume to be completed before his death. Marx's friend and collaborator Friedrich Engels (1820–1895) edited and published volumes two and three after Marx's death.

Marx had several important intellectual influences. One of his primary influences comes from the work of G.W.F. Hegel. Hegel's theory presents history as a process of the world becoming conscious of itself as spirit. Marx took this idea and instead argued that it was man that was alienated from himself in the material world. Escape from this alienation requires a revolution. Marx also responds to the economic theories that were dominant in his time. He addresses several economists by name, such as Adam Smith and John Stuart Mill.

Marx's theory should be understood in the context of the hardships suffered by 19th century workers in England, France and Germany. The Industrial Revolution of the 18th and 19th centuries created a seemingly permanent underclass of workers, many of whom lived in poverty under terrible working conditions and with little political representation. Capital was based on thirty years of studying capitalism in England, which was the most advanced industrial society in Marx's time. Based on these observations, Marx developed a complex theory about the structure and function of capitalism.