Tolstoy (Russian: Толстой) is a noble Russian family name derived from the Russian adjective то́лстый (tolsty; 'thick, stout, fat').
The family name is shared by three major Russian writers of the 19th–20th centuries, of whom two also share first names Alexei, and one of these has the same patronymic Nikolaevich (Nicholas's son) with the best known of them — Lev or Leo Tolstoy (1828–1910).
Tolstoy (Rus. masculine), Tolstaya (Rus. feminine), or Tolstoye (Rus. neuter) may also refer to: