Achaemenes was the eponymous ancestor of the royal house of the first Persian Empire, the Achaemenid dynasty. He lived around 700 BC. His name comes from the Old Persian Hakhāmanish, meaning "friendly in nature." The name's Hellenized form is Achaimenēs, which has become rendered in English as Achaemenes. Achaemenes did not rule all of Iran, but a small kingdom in the western part of the country near Lake Urmia, which Assyrian inscriptions call Parsumash, or land of the Parsu or Persians.

Achaemenes' royal descendents revered him and credited him as the founder of their dynasty, but very little was ever remembered about his specific achievements. Most likely he was a warrior chieftain who led the Persians as a vassal of the Median Empire. An Assyrian inscription from the time of King Sennacherib mentions that the Assyrian king repelled a raid by the Parsu, which may have been led by Achaemenes. Plato, when writing about the Persians, oddly speculated that Achaemenes was the son of the Greek hero Perseus and a grandson of Zeus.

Achaemenes was succeeded by his son Teispes , who would lead the Persians to conquer and settle in the city of Anshan. His great-grandson was Cyrus II, who conquered the Medes and established the Persian Empire.

Due to the lack of hard information on Achaemenes, it has been contended that epigraphic evidence for his existence and rule is highly suspect; in fact, he may have been an invention of Darius the Great.

The name Achaemenes is also borne by a son of Darius I, brother of Xerxes I. After the first rebellion of Egypt, he became satrap of Egypt (484 BC); he commanded the Persian fleet at Salamis Island, and was (460 BC) defeated and slain by Inarus, the leader of the second rebellion of Egypt.

A man called Achaemenes is a minor character in Virgil's Aeneid. His character seems to have been chosen by Virgil treating the name Achaemenes as Greek and extracting a meaning "he who waits with affliction".