Achaemenid Ruling dynasty of the first Persian Empire, which stretched from the River Nile as far e as modern Afghanistan. The dynasty was founded by Cyrus the Great (r.559–529 bc) and named after his ancestor Achaemenes. Darius I (r.521–486 bc) decentralized government administration. The last Achaemenid ruler, Darius III (r.336–330 bc), was defeated by Alexander the Great. The dynasty was responsible for the spread of Zoroastrianism through Asia, and the remains at Persepolis are testimony to the splendour of Persian art and architecture at this time.

Achaemenid a member of the dynasty ruling in Persia from Cyrus I to Darius III (553–330 bc); the name comes from Greek Akhaimenēs ‘Achaemenes’, the reputed ancestor of the dynasty.