Semyaza, also known as Ouza, Samiaza, Shemhazai, Amezyarak, Azza, and Uzza was a major leader of the fall from heaven in Christian mythology. He was also one of the angels that came down from heaven alongside Azazel to interbreed with humans. Semyaza before the fall was of the rank of Seraphim. In legend, he is the seraph tempted by the maiden Ishtahar to reveal to her the Explicit Name of God. Often it is speculated that a main reason for Semyaza's expulsion from heaven is that he objected to the high rank given to Enoch when the latter was transformed from a mortal into the angel Metatron. In Solomonic lore the story is that Semyaza was the angel who revealed to the Jewish king the heavenly arcana, thus making Solomon the wisest man on earth. Of the 2 groups of angels headed by Metatron, one of the groups, the angels of justice, were under the rulership of Semyaza, who at this time had not yet fallen. Uzza is the tutelary angel of the Egyptians. The name Semyaza means literally "the name Azza."

Semyaza's sons, Hiwa and Hiya, by one of Eve's daughters, were so mighty that they daily ate 1000 camels, 1000 horses, and 1000 oxen.