The Decline of the West (German: Der Untergang des Abendlandes) is a two-volume work by Oswald Spengler, the first volume of which was published in the summer of 1918. Spengler revised this volume in 1922 and published the second volume, subtitled Perspectives of World History, in 1923.

The book includes the idea of the Islamics being Magian, Greeks being Apollinian, and the Westerners being Faustian, and according to its theories we are now living in the winter time of the Faustian civilization.