Friedrich Engels was a German philosopher, political theorist, historian, journalist, and revolutionary socialist. He is widely known as Karl Marx's lifelong friend and closest collaborator, serving as a leading authority on Marxism.

Engels, the son of a wealthy textile manufacturer, met Marx in 1844. They jointly authored several significant works, including The Holy Family (1844), The German Ideology (1846), and The Communist Manifesto (1848). Engels was instrumental in supporting Marx financially, which enabled Marx to continue writing after moving to London in 1849. After Marx's death in 1883, Engels edited the manuscripts and completed Volumes II and III of Das Kapital (1885 and 1894).

Engels wrote several important works of his own, including The Condition of the Working Class in England (1845), Anti-Dühring (1878), Dialectics of Nature (1878–1882), The Origin of the Family, Private Property and the State (1884), and Ludwig Feuerbach and the End of Classical German Philosophy (1886).