Hormizd I was the third Sassanid King of Persia from 270/72 to 273.

He was the son of Shapur I (240-270/72); under whom he was governor of Khorasan; and appears in his wars against Rome (Historia Augusta; Trig. Tyr. 2; where N鰈deke has corrected the name Odomastes into Oromastes; i.e. Hormizd).

In the Persian tradition of the history of Ardashir I (226-240 [died 241/42]); preserved in a Pahlavi text (N鰈deke; Geschichte des Artachsir I. Papakan); Hormizd I is made the son of a daughter of Mithrak; a Persian dynast; whose family Ardashir had extirpated because the Magi had predicted that the restorer of the empire of Persia would come from his blood.

According to legend; this daughter alone was saved by a peasant; Shapur I saw her and made her his wife; and afterwards her son Hormizd I was recognized and acknowledged by Ardashir. In this legend; which has also been partially preserved in Tabari; the great conquests of Shapur I are transferred to Hormizd I. In reality he reigned only one year and ten days.