Arsaces II, also Artabanus I, of the Arsacid dynasty was King of Parthia

Parthia

Parthia is a region of north-eastern Iran, best known for having been the political and cultural base of the Arsacid dynasty, rulers of the Parthian Empire....

 between 211 BC and 191 BC. Greek 'Arsaces' appears as 'Artabanus' in Latin sources, and both forms appear in history books.

Due to a confusion of names, the line of succession is equally unclear. Artabanus's uncle, Arsaces I, had founded the dynasty around 247 BC. Arsaces I may then have been directly succeeded by his brother Tiridates I

Tiridates I of Parthia

Tiridates, or Teridates is a Persian name, given by Arrian in his Parthica to the brother of Arsaces I, the founder of the Parthian kingdom, whom he is said to have succeeded in about 246 BC...

, who however -
like all other Arsacid dynasts also - adopted the name Arsaces upon his coronation. Subject then to which genealogy is followed (neither is epigraphically assured), Artabanus (a.k.a. Arsaces II) succeeded either his uncle Arsaces I or his father Tiridates I (a.k.a. Arsaces II).

In 209 BC, the Seleucid King Antiochus III recaptured Parthia, which had been previously seized from the Seleucids by the Arsaces I and the Parni

Parni

The Parni or Aparni were an east Iranian people of the Ochus River valley, southeast of the Caspian Sea...

 around 247 BC. Arsaces II sued for peace following his defeat on the battlefield at Mount Labus.

In the terms of peace, Arsaces accepted feudatory status and from then onwards ruled Parthia and Hyrancia as a vassal state of the Seleucids. Antiochus in turn withdrew his troops westwards, where he would subsequently be embroiled in wars with Rome and so would leave the fledgling Parthian kingdom to its own devices.

Arsaces II was succeeded by his son (or cousin) Phriapatius

Phriapatius of Parthia

Phriapatius , sometimes called Phriapites, ruled the Parthian Empire from 191 BC to 176 BC. He was the grandson of Tiridates I of Parthia , the brother of Arsaces I of Parthia , the founder of the Parthian Empire.He ruled in the period following the invasion of Parthia by the Seleucid king...

 in 191 BC.