What Is to be Done? (sometimes translated as What Then Must We Do?) is a non-fiction work by Leo Tolstoy, in which Tolstoy describes the social conditions of Russia in his day. Tolstoy completed the book in 1886, and the first English language publication came in 1887 as What To Do?. A revised translation with the current title was published in 1899.

The English title was also used for two better-known works by Nikolai Chernyshevsky and Vladimir Lenin; Tolstoy's Russian title is similar but not identical to Chernyshevsky's (and [[What Is to Be