Perennial Philosophy is a term that is often used as a synonym for Sanatana Dharma (Sanskrit for "Eternal or Perennial Truth"). It was used by Leibniz to designate the common, eternal philosophy that underlies all religious movements, in particular the mystical streams within religions. The term was popularized by Aldous Huxley in his 1945 book The Perennial Philosophy in his description of Vedanta.

The concept is the fundamental tenet of the Traditionalist School, formalized in the writings of 20th century metaphysicians Rene Guenon and Frithjof Schuon.