Madai was one of the sons of Japheth, who was the son of Noah. He is traditionally regarded as the ancestor of the Medes, the people who founded the Median Empire in ancient Iran. His name appears in the Bible's genealogies as part of the origins of nations after the flood.
In the Table of Nations in Genesis 10, it is described how Noah's descendants became various peoples and nations, and Madai is linked to the Medes who settled in northwestern Iran.
The Medes, who were traditionally regarded as descendants of Madai, play an important role in the Bible's prophecies, especially in Isaiah's prophecy about the fall of Babylon.
The prophet Daniel describes how the Medo-Persian empire took power from Babylon, which is linked to Madai's descendants as a mighty people in world history.
28PERES—your kingdom has been divided and given to the Medes and Persians." [Footnote: PERES sounds like the Aramaic word for 'divided' and also like the name 'Persia.']