Nikolay Onufriyevich Lossky, also known as N. O. Lossky, was a Russian philosopher, representative of Russian idealism, intuitionist epistemology, personalism, libertarianism, ethics and axiology. He gave his philosophical system the name intuitive-personalism. Born in Latvia, he spent his working life in St. Petersburg, New York, and Paris. He was the father of the influential Christian theologian Vladimir Lossky.

Gnosiology is "the philosophy of knowledge and cognition". In Italian, Soviet and post-Soviet philosophy, the word is often used as a synonym for epistemology. The term is also currently used in regard to Eastern Christianity.