Marxist philosophy or Marxist theory are terms that cover work in philosophy that is strongly influenced by Karl Marx's materialist approach to theory or that is written by Marxists. It may be broadly divided into Western Marxism, which drew out of various sources, and the official philosophy in the Soviet Union, which enforced a rigid reading of Marx called "diamat" (for "dialectical materialism"), in particular during the 1930s.

The phrase "Marxist philosophy" itself does not indicate a strictly defined sub-field of philosophy, because the diverse influence of Marxist theory has extended into fields as varied as aesthetics, ethics, ontology, epistemology, and philosophy of science, as well as its obvious influence on political philosophy and the philosophy of history. The key characteristics of Marxism in philosophy are its materialism and its commitment to political practice as the end goal of all thought.

Louis Althusser, for example, defined philosophy as "class struggle in theory", thus radically separating himself from those who claimed philosophers could adopt a "God's eye view" as a purely neutral judge. Just as the young Marx had left university and German Idealism to encounter the proletariat, which permitted him to modify his perspective on practice and theory, "intellectuals" couldn't content themselves with instructing the masses from their chairs (as the "organic intellectual" conception denounced by Antonio Gramsci) but personally had to take part in the social struggles of their times.

Terence Francis Eagleton FBA (born 22 February 1943, Salford) is a British literary theorist and critic, who is regarded as one of Britain's most influential living literary critics. Eagleton currently serves as Distinguished Professor of English Literature at the Lancaster University, and as a former Visiting Professor at the National University of Ireland, Galway.

Formerly Eagleton was Thomas Warton Professor of English Literature at the University of Oxford (1992–2001) and John Edward Taylor Professor of English Literature at the University of Manchester until 2008. In the Fall 2009 semester, Dr Eagleton returned to the University of Notre Dame as a Distinguished Visitor in the Department of English.

He has written more than forty books, including Literary Theory: An Introduction (1983);The Ideology of the Aesthetic (1990), and The Illusions of Postmodernism (1996).

Professor Eagleton delivered Yale University's 2008 Terry Lectures and gave a Gifford Lecture in March 2010, titled The God Debate. He gave the 2010 Richard Price Memorial Lecture at the historically radical Newington Green Unitarian Church, speaking on "The New Atheism and the War on Terror".

Peter Albert David Singer (born 6 July 1946) is an Australian philosopher who is the Ira W. DeCamp Professor of Bioethics at Princeton University and Laureate Professor at the Centre for Applied Philosophy and Public Ethics at the University of Melbourne. He specialises in applied ethics and approaches ethical issues from a secular, preference utilitarian perspective.

He has served, on two occasions, as chair of philosophy at Monash University, where he founded its Centre for Human Bioethics. In 1996, he unsuccessfully stood as a Greens candidate for the Australian Senate. In 2004, he was recognised as the Australian Humanist of the Year by the Council of Australian Humanist Societies. He has been voted one of Australia's ten most influential public intellectuals. Singer serves on the Advisory Board of Incentives for Global Health, the NGO formed to develop the Health Impact Fund proposal.

Outside academic circles, Singer is best known for his book Animal Liberation, widely regarded as the touchstone of the animal liberation movement. Not all members of the animal liberation movement share this view, and Singer himself has said the media overstates his status. His views on that and other issues in bioethics have attracted attention and a degree of controversy.

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 and 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, and also campaigned for socialism—he became a significant figure in the International Workingmen's Association.