Darius I lived from 550 BC until 486 BC. He ruled over the Persian Empire at it's peak with control over territory from Greece to near India.
Darius began the attempted first invasion of Greece after the Ionian Revolt. This ended with the defeat of the Persians at the Battle of Marathon in 490 BC. He died before beginning a second invasion which was taken up by his son Xerxes I.
Much of what is known about the life of Darius I comes from monuments and the writings of Herodotus.
Darius is mentioned in several books of the Bible most notably the books of Ezra and Nehemiah which concern the return of the people of Israel to their ancestral land after the conquest of Babylon by the Persians.