"Religion is the opium of the people" is one of the most frequently paraphrased statements of German philosopher and economist Karl Marx. It was translated from the German original, "Die Religion ... ist das Opium des Volkes" and is often rendered as "religion... is the opiate of the masses."
The quotation originates from the introduction of Marx's work A Contribution to the Critique of Hegel's Philosophy of Right, which he started in 1843 but which was not published until after his death. The introduction to this work was published separately in 1844, in Marx's own journal Deutsch–Französische Jahrbücher, a collaboration with Arnold Ruge.
The full quote from Karl Marx translates as: "Religion is the sigh of the oppressed creature, the heart of a heartless world, and the soul of soulless conditions. It is the opium of the people". Often quoted only in part, the interpretation of the metaphor in its context has received much less attention.
Some other people have used similar phrases.
The quotation, in context, reads as follows (emphasis added):
The foundation of irreligious criticism is: Man makes religion, religion does not make man. Religion is, indeed, the self-consciousness and self-esteem of man who has either not yet won through to himself, or has already lost himself again. But man is no abstract being squatting outside the world. Man is the world of man – state, society. This state and this society produce religion, which is an inverted consciousness of the world, because they are an inverted world. Religion is the general theory of this world, its encyclopaedic compendium, its logic in popular form, its spiritual point d’honneur, its enthusiasm, its moral sanction, its solemn complement, and its universal basis of consolation and justification. It is the fantastic realization of the human essence since the human essence has not acquired any true reality. The struggle against religion is, therefore, indirectly the struggle against that world whose spiritual aroma is religion.
Religious suffering is, at one and the same time, the expression of real suffering and a protest against real suffering. Religion is the sigh of the oppressed creature, the heart of a heartless world, and the soul of soulless conditions. It is the opium of the people.