Hormizd III (Persian: هرمز سوم), was the seventeenth king of the Sasanian Empire. He was the son and successor of Yazdegerd II (438–457).
In 457, Yazdegerd II died. Hormizd, the older son of Yazdegerd II, was kept near Ctesiphon, while his younger brother, Peroz, was stationed in Sistan. Following his father's death, Hormizd became ruler of the Sassanian Empire. In response, Peroz sought the aid of the Hephthalite monarch, Khushnavaz in Bactria. The Hephthalites aided Peroz, who defeated Hormizd and by 459 controlled Ctesiphon making him ruler of the Sassanian Empire.
Sources differ as to what happened to Hormizd after his capture. Some say that he was put to death in 459. However, the Persian historian Mirkhond says that Peroz pardoned his eldest brother and amicably spared his life.
Hormizd III had a daughter named Balendukht, who was the wife of Vakhtang I, the ruler of Iberia. She bore the latter a son named Dachi.