Pyotr Demianovich Ouspenskii (known in English as Peter D. Ouspensky; Russian: Пётр Демьянович Успенский, romanized: Pyotr Dem'yanovich Uspenskiy; 5 March 1878 – 2 October 1947), was a Russian esotericist known for his expositions of the early work of the Greek-Armenian teacher of esoteric doctrine George Gurdjieff. He met Gurdjieff in Moscow in 1915, and was associated with the ideas and practices originating with Gurdjieff from then on. He taught ideas and methods based in the Gurdjieff system for 25 years in England and the United States, although he separated from Gurdjieff personally in 1924, for reasons that are explained in the last chapter of his book In Search of the Miraculous.