The slogan "Workers of the world, unite!" is attributed to Karl Marx and is featured in "The Communist Manifesto." This call to action reflects the core tenet of Marxist ideology, advocating for the solidarity of the working class across national borders to overthrow capitalist systems. It emphasizes the shared struggles of workers against exploitation and the pursuit of a classless society. Marx's ideas inspired labor movements and revolutions throughout the 19th and 20th centuries, encouraging workers to recognize their collective power and fight for their rights globally.