Mazyar (Persian: مازیار‎) was an Iranian aristocrat of the House of Karen and feudal ruler of the mountainous region of Tabaristan (present-day Mazandaran, Iran). For his resistance to the Baghdad Caliphate, Maziar is considered one of the national heroes of Greater Iran by twentieth-century Iranian nationalist historiography, who have recast his struggle as one against Arab invaders.

Mazyar, a devout Zoroastrian, revolted against the Abbasid Caliphate in the 9th century CE. His revolt began in 839 AD during the rule of Al-Mu'tasim. Along with Babak Khorramdin, he repulsed many armies sent against him.

According to the medieval historian Ibn Esfandyar in his Tarikh-e-Tabaristan, Mazyar is said to have proclaimed: "Afshin Kheydar, son of Kavus and Babak, and I had made an oath and allegiance that we take the country back from the Arabs and transfer the government and the country back to the family of Kasraviyan."

Mazyar was eventually betrayed by his brother Kuhyar and captured by the Caliph's forces. He was imprisoned in Baghdad awaiting execution when he drank poison and ended his life in order to avoid humiliation at the hands of the Caliph's executioners.