Tahmuras or Tahmures was the third Shah of the mythical Pishdadian dynasty of Iran according to Ferdowsi's epic poem, the Shahnameh. He is considered the builder of Merv.

The Pishdadian dynasty is a mythical line of primordial kings featured in Zoroastrian belief and Persian mythology. They are presented in legend as originally rulers of the world but whose realm was eventually limited to Ērānshahr or Greater Iran. Although there are scattered references to them in the Zoroastrian scriptures—the Avesta—and later Pahlavi literature, it is through the 11th-century Iranian national epic, the Shahnameh, that the canonical form of their legends is known. From the 9th century, Muslim writers, notably Tabari, re-told many of the Pishdadian legends in prose histories and other works. The Pishdadian kings and the stories relating to them have no basis in historical fact, however.