Darius I, titled "Darius the Great," was the third king of kings of the Achaemenid Empire. Darius held the empire at its peak, then including Egypt, and parts of Greece. The decay and downfall of the empire commenced with his death and the coronation of his son, Xerxes I.

Darius ascended the throne by assassinating the alleged usurper Gaumata with the assistance of six other Persian noble families; Darius was crowned the following morning. The new emperor met with rebellions throughout his kingdom, and quelled them each time. A major event in Darius' life was his expedition to punish Athens and Eretria and subjugate Greece. Darius expanded his empire by conquering Thrace and Macedon, and invading the Saka, Iranian tribes who had invaded Medes even killed Cyrus the Great.

Darius organized the empire, by dividing it into provinces and placing governors to govern it. He organized a new monetary system, along with making Aramaic the official language of the empire. Darius also worked on construction projects throughout the empire, focusing on Susa, Babylon, and Egypt. Darius created a codification of laws for Egypt. He also carved the cliff-face Behistun Inscription, an autobiography of great modern linguistic significance.