The Decline of the West (German: Der Untergang des Abendlandes; more literally, The Downfall of the Occident or even more literally, "The Going-Under of the Evening Lands") is a two-volume work by Oswald Spengler. The first volume, subtitled Form and Actuality, was published in the summer of 1918. The second volume, subtitled Perspectives of World History, was published in 1922. The definitive edition of both volumes was published in 1923.
Spengler introduced his book as a "Copernican overturning"—a specific metaphor of societal collapse—involving the rejection of the Eurocentric view of history, especially the division of history into the linear "ancient-medieval-modern" rubric. According to Spengler, the meaningful units for history are not epochs but whole cultures which evolve as organisms. In his framework, the terms "culture" and "civilization" were given non-standard definitions, and cultures are described as having lifespans of about a thousand years of flourishing, and a thousand years of decline.