Who was the Persian king at the time of the Ionian Revolt?

The Persian king at the time of the Ionian Revolt (which began in 499 BCE) was Darius I, also known as Darius the Great. He ruled from 522 to 486 BCE and sought to consolidate and expand the Persian Empire. The revolt, initiated by the Ionian city-states against Persian rule, ultimately led to significant conflicts between Persia and Greece, including the Greco-Persian Wars. Darius's efforts to suppress the revolt laid the groundwork for these larger confrontations.