The author of "The Communist Manifesto" in the 19th century was Karl Marx, alongside Friedrich Engels. Published in 1848, the manifesto is a political pamphlet that presents an analytical approach to the class struggles and the problems of capitalism. It famously advocates for the working class, or proletariat, to unify and rise against capitalist oppression. The document has significantly influenced political movements worldwide and is considered one of the foundational texts of communist ideology. Marx’s ideas, particularly concerning class struggle, labor, and historical materialism, shaped various political theories and movements throughout the 20th century.