The Reign of Quantity and the Signs of the Times (French: Le Règne de la Quantité et les Signes des Temps) is a 1945 book by the French intellectual René Guénon, in which the author offers a comprehensive explanation, based on tradition, of the cyclical conditions that led to the modern world in general and to the Second World War in particular.

Jacob Needleman, in The Sword of Gnosis, writes:"Many of Guénon's books, notably The Reign of Quantity, are such potent and detailed metaphysical attacks on the downward drift of Western civilisation as to make all other contemporary critiques seem half-hearted by comparison.

"Harry Oldmeadow, author of Traditionalism: Religion in the Light of the Perennial Philosophy:"The Reign of Quantity is a brilliantly sustained and excoriating attack on modern civilisation [...] The book is a controlled and dispassionate but devastating razing of the assumptions and values of modern science.

At the same time it is an affirmation of the metaphysical and cosmological principles given expression in traditional culture and religions.

"[1]There are complete translations of Le règne de la quantité in a number of languages: English, Italian, Spanish, Swedish, Persian, and Turkish.