Workers of all countries, unite!

The political slogan Workers of the world, unite! is one of the most famous rallying cries from the Communist Manifesto (1848), by Karl Marx and Friedrich Engels (German: Proletarier aller Länder vereinigt Euch!, literally "Proletarians of all countries, unite!" but soon popularized in English as "Workers of the world, unite! You have nothing to lose but your chains!") A variation of this phrase ("Workers of all lands, unite") is also inscribed on Marx's tombstone. The essence of the slogan is that members of the working classes throughout the world should cooperate to achieve victory in class conflict.

Five years before the Communist Manifesto, the phrase appeared in the 1843 book "The Workers' Union" by Flora Tristan.

The International Workingmen's Association, described by Engels as "the first international movement of the working class" was persuaded by Engels to change its motto from the League of the Just's "all men are brothers" to "working men of all countries, unite!" It reflected Marx's and Engels' view of proletarian internationalism.

The phrase has overlapping meanings. First that workers should unite in unions to better push for their demands such as workplace pay and conditions. Secondly, that workers should see beyond their various craft unions and unite against the capitalist system. And thirdly, that workers of different countries have more in common with each other than workers and employers of the same country.

The phrase was used by the Industrial Workers of the World (IWW) in their publications and songs, and was a mainstay on banners in May Day demonstrations. The IWW used it when opposing World War I in both the USA and Australia.

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