Karl Heinrich Marx (5 May 1818 – 14 March 1883) was a German philosopher, economist, sociologist, historian, journalist, and revolutionary socialist. His ideas played a significant role in the development of social science and the socialist political movement. He published various books during his lifetime, with the most notable being The Communist Manifesto (1848) and Capital (1867–1894); some of his works were co-written with his friend, the fellow German revolutionary socialist Friedrich Engels.
Born into a wealthy middle class family in Trier, formerly in Prussian Rhineland now called Rhineland-Palatinate, Marx studied at both the University of Bonn and the University of Berlin, where he became interested in the philosophical ideas of the Young Hegelians. In 1836, he became engaged to Jenny von Westphalen, marrying her in 1843. After his studies, he wrote for a radical newspaper in Cologne, and began to work out his theory of dialectical materialism. Moving to Paris in 1843, he began writing for other radical newspapers. He met Engels in Paris, and the two men worked together on a series of books. Exiled to Brussels, he became a leading figure of the Communist League, before moving back to Cologne, where he founded his own newspaper. In 1849 he was exiled again and moved to London together with his wife and children. In London, where the family was reduced to poverty, Marx continued writing and formulating his theories about the nature of society and how he believed it could be improved, as well as campaigning for socialism and becoming a significant figure in the International Workingmen's Association.
Marx's theories about society, economics and politics, which are collectively known as Marxism, hold that all societies progress through the dialectic of class struggle; a conflict between an ownership class which controls production and a lower class which produces the labour for such goods. Heavily critical of the current socio-economic form of society, capitalism, he called it the "dictatorship of the bourgeoisie", believing it to be run by the wealthy classes purely for their own benefit, and predicted that, like previous socioeconomic systems, it would inevitably produce internal tensions which would lead to its self-destruction and replacement by a new system, socialism. He argued that under socialism society would be governed by the working class in what he called the "dictatorship of the proletariat", the "workers state" or "workers' democracy". He believed that socialism would, in its turn, eventually be replaced by a stateless, classless society called communism. Along with believing in the inevitability of socialism and communism, Marx actively fought for the former's implementation, arguing that both social theorists and underprivileged people should carry out organised revolutionary action to topple capitalism and bring about socio-economic change.
Revolutionary socialist governments espousing Marxist concepts took power in a variety of countries in the 20th century, leading to the formation of such socialist states as the Soviet Union in 1922 and the People's Republic of China in 1949, while various theoretical variants, such as Leninism, Stalinism, Trotskyism and Maoism, were developed. Marx is typically cited, with Émile Durkheim and Max Weber, as one of the three principal architects of modern social science. Marx has been described as one of the most influential figures in human history, and in a 1999 BBC poll was voted the top "thinker of the millennium" by people from around the world.