WORKERS OF THE WORLD, UNITE! is the anglicised slogan of the concluding lines of karl Marx and Freidrich Engels pamphlet The Communist Manifesto, the original being, "WORKING MEN OF ALL COUNTRIES, UNITE!".
The phrase is often used as a propaganda slogan by communist groups from every strain of Marxist from Marxism_Leninism tp Trotskyism. The phrase has also been used as a general left wing phrase for international working solidarity.