The Arsacid Dynasty ruled Persia. Their realm is also called Parthia, which included the Iranian plateau and intermittently Mesopotamia, from 253 BC until their overthrow by the Sassanid Dynasty in AD 226.
Parthia was led by the Arsacid dynasty, who reunited and ruled over the Iranian plateau, taking over the eastern provinces of the Greek Seleucid Empire, beginning in the late 3rd century BCE, and intermittently controlled Mesopotamia between ca 150 BCE and 224 CE.
Courtiers spoke Persian and used the Pahlavi script; the royal court traveled from capital to capital, and the Arsacid kings styled themselves "king of kings".
Their power now rivaled the king's, while at the same time internal divisions in the Arsacid family had rendered them vulnerable.
In time Phraates succeeded to the throne of the Arsacids and, by calling for aid from the Romans, caused the overthrow of Tigranes; but the haughty republic of the West granted its assistance with such ill grace that years of warfare resulted.
The founder of the Sassanian dynasty, Ardashir Papakan (Artaxerxes, son of Papak), was born at Persis, in central Iran; his family claimed descent from a mythical ancestor, Sassan, and he was therefore of the priestly caste.
Vologeses V, the last king of the Arsacid dynasty of Parthia, declared war against the rising chief, but was defeated and put to death by Ardashir A.D. Thus the Parthian Empire passed into the hands of the Sassanian dynasty.