The term Persian King can refer to four different rulers: Xerxes (6 letters), DARIUS (6 letters), CYRUS (5 letters), and SHAH (4 letters). Xerxes was the fourth king of the Achaemenid Empire, ruling from 486 to 465 BC. DARIUS was the third king of the Achaemenid Empire, ruling from 522 to 486 BC. CYRUS was the founder of the Achaemenid Empire, ruling from 550 to 530 BC. SHAH is a title given to Persian kings, and Artaxerxes (10 letters) was the sixth king of the Achaemenid Empire, ruling from 465 to 424 BC.