Arsaces I of Parthia was the chief of the Parni, one of the nomadic Scythian or Dahan tribes in the desert east of the Caspian Sea. A later tradition, preserved by Arrian, derives Arsaces I and his brother Tiridates from the Achaemenian king Artaxerxes II, but this has evidently no historical value.

Arsaces, seeking refuge before the Bactrian king Diodotus I, invaded Parthia, then a province of the Seleucid Empire, in about 250 BC. According to Arrian he was then killed and was succeeded by his brother. But modern historians believe that he ruled Parthia until 211 BC, when he was succeeded by his son Arsaces II.

After him all the other Parthian kings of the Arsacid Dynasty, amounting to the number of about thirty, officially wear only the name Arsaces.

With very few exceptions only the name Αρσακης occurs on the coins of the Parthian kings (in its genitive form ΑΡΣΑΚΟΥ — i.e., "[coin] of Arsaces" — together with various epithets), and the obverse generally shows the seated figure of the founder of the dynasty, holding in his hand a strung bow. The Parthian Empire was finally overthrown in AD 226 by Ardashir I (Artaxerxes), the founder of the Sassanid Dynasty.

References

• Strabo, xi.
• Arrian, i (preserved in Photius and Syncellus).