Leo Tolstoy, or Count Lev Nikolayevich Tolstoy (Russian: Лев Никола́евич Толсто́й (help·info), Russian pronunciation: ; September 9 1828 – November 20 1910), was a Russian writer widely regarded as among the greatest of European novelists. His masterpieces, War and Peace and Anna Karenina, represent the peak of realist fiction in their scope, breadth and vivid depiction of 19th-century Russian life and mind.

Tolstoy's further talents as essayist, dramatist, and educational reformer made him the most influential member of the aristocratic Tolstoy family. His literal interpretation of the ethical teachings of Jesus, centering on the Sermon on the Mount, caused him in later life to become a fervent Christian anarchist and pacifist. His ideas on nonviolent resistance, expressed in such works as The Kingdom of God Is Within You, were to have a profound impact on such pivotal twentieth-century figures as Gandhi and Martin Luther King, Jr.

Tolstoy was born in Yasnaya Polyana, the family estate situated in the region of Tula, Russia. The Tolstoys are a well-known family of old Russian nobility, and he was connected to the grandest families of Russian aristocracy; Alexander Pushkin was his fourth cousin.