Mithridates I of Parthia

Mithridates I (also spelled Mithradates I or Mihrdad I), also known as Mithridates I the Great, was king of the Parthian Empire from 171 BCE to 132 BCE. During his reign, Parthia was transformed from a small Seleucid client state into a major political power in the Ancient East as a result of his conquests. He first conquered Aria, Margiana and western Bactria from the Greco-Bactrians sometime in 163–155 BCE, and then waged war with the Seleucid Empire, conquering Media and Atropatene in 148/7 BCE. In 141 BCE, he conquered Babylonia and held an official investiture ceremony in Seleucia. The kingdoms of Elymais and Characene shortly afterwards became Parthian vassals. In c. 140 BCE, while Mithridates was fighting the nomadic Saka in the east, the Seleucid king Demetrius I Soter attempted to regain the lost territories; initially successful, he was defeated and captured in 138 BCE, and shortly afterwards sent to one of Mithridates I's palaces in Hyrcania. Mithridates I then punished Elymais for aiding Demetrius, and made Persis a Parthian vassal.

Mithridates I was the first Parthian king to assume the ancient Achaemenid title of King of Kings. Due to his accomplishments, he has been compared to Cyrus the Great ( r . 550–530 BCE), the founder of the Achaemenid Empire. Mithridates I died in 132 BCE, and was succeeded by his son Phraates II.

Source
https://en.wikipedia.org/wiki/Mithridates_I_of_Parthia