Isaiah, Hebrew Yeshaʿyahu (“God Is Salvation”) (flourished 8th century bc, Jerusalem), prophet after whom the biblical Book of Isaiah is named (only some of the first 39 chapters are attributed to him), a significant contributor to Jewish and Christian traditions. His call to prophecy in about 742 bc coincided with the beginnings of the westward expansion of the Assyrian empire, which threatened Israel and which Isaiah proclaimed to be a warning from God to a godless people.