War and Peace (pre-reform Russian: Война́ и миръ (War and Society); post-reform Russian: Война́ и мир) is a novel by the Russian author Leo Tolstoy, which is regarded as a central work of world literature and one of Tolstoy's finest literary achievements.

The novel chronicles the history of the French invasion of Russia and the impact of the Napoleonic era on Tsarist society through the stories of five Russian aristocratic families. Portions of an earlier version, titled The Year 1805, were serialized in The Russian Messenger from 1865 to 1867. The novel was first published in its entirety in 1869.

Tolstoy said War and Peace is "not a novel, even less is it a poem, and still less a historical chronicle". Large sections, especially the later chapters, are a philosophical discussion rather than narrative. Tolstoy also said that the best Russian literature does not conform to standards and hence hesitated to call War and Peace a novel. Instead, he regarded Anna Karenina as his first true novel. According to the Encyclopædia Britannica, "no single English novel attains the universality of Leo Tolstoy's War and Peace."