War and Peace 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. War and Peace is perhaps best known as one of the longest novels ever written.

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.

The novel spans the period 1805 to 1820. The era of Catherine the Great was still fresh in the minds of older people. Catherine had made French the language of her royal court. For the next one hundred years, it became a social requirement for members of the Russian nobility to speak French and understand French culture. This historical and cultural context in the aristocracy is reflected in War and Peace. Catherine's grandson, Alexander I, came to the throne in 1801 at the age of 24. In the novel, his mother, Marya Feodorovna, is the most powerful woman in the Russian court.