Mithridates I or Mithradates (c.195 BC - 138 BC) was the "Great King" of Parthia from 171 BC to 138 BC, succeeding his brother Phraates I. He was the son of Priapatius, King of Parthia (died 176 BC). He made Parthia into a major political power, expanded the empire westward into Mesopotamia. During his reign, the Parthians took Babylonia (144 BC), Media (141 BC) and Persia (139 BC), when Mithridates captured the Seleucid ruler Demetrius II of Syria. Demetrius later married Mithridates's daughter Rhodogune.
Eastward Mithridates extended his control into Margiana, Aria and Bactria, thus completing Parthian control of the overland trade routes between east and west, the Silk Road and the Persian Royal Road. This control of trade was to be the foundation of Parthian wealth and power, and was jealously guarded by the Arsacids, who always attempted to maintain direct control over the lands through which the major trade routes passed.
Parthian control broke the tenuous link with Greeks in the West that had sustained the Hellenistic kingdom of Bactria, yet Mithradates actively promoted Hellenism in the areas he controlled and titled himself Philhellene ("friend of the Greeks") on his somewhat primitive coins: they show the first appearance on Parthian coins of a Greek-style portrait showing the royal diadem, the standard Greek symbol for kingship.. Mithradates resumed the striking of coins, which had been suspended ever since Arsaces II (211-191 BC) had been forced to submit to the SeleucidAntiochus III in 206.
His name assigned him to the protection of Mithra and carried the god's authority in some measure.
His son Phraates succeeded him on his death as King.
Mithridates VI (114- 63 B.C.) or Mithridates Eupator is the king who caused Rome so much trouble during the time of Sulla and Marius.
Mithridates, who ruled from 120-63 is said to have ingested a little bit of all the known poisons (a universalantidote) each day starting early in his life.
The conflict with Rome that was to last for the rest of Mithridates' life became inevitable in 94, when Nicomedes III of Bithynia died and was succeeded by Nicomedes IV Philopator.
In the summer, Mithridates was invited by the Athenians to liberate them from the Romans, and he sent his armies across the Aegean.
Mithridates was again forced to flee to Armenia, but this time, his ally was unable to help him.