Friedrich Engels (German: [ˈfʁiːdʁɪç ˈɛŋəls]; 28 November 1820 – 5 August 1895) was a German social scientist, author, political theorist, philosopher, and father of Marxist theory, together with Karl Marx. In 1845 he published The Condition of the Working Class in England, based on personal observations and research in Manchester.

In 1848 he co-authored The Communist Manifesto with Karl Marx, though he has also authored and co-authored (primarily with Marx) many other works, and later he supported Marx financially to do research and write Das Kapital. After Marx's death, Engels edited the second and third volumes. Additionally, Engels organized Marx's notes on the "Theories of Surplus Value," which he later published as the "fourth volume" of Capital. He has also made important contributions to family economics.

1. ^ Theories of Surplus Value, in Collected Works of Marx and Englels: Volumes 30, 31 and 32 (International Publishers: New York, 1988).