Priapatius, was the Arsacid king of Parthia from 191 BC to 176 BC. He was the first-cousin-once-removed and successor of Arsaces II. Like many Arsacid monarchs, his reign is sparsely known. His coinage indicates that he managed to rid himself of the influence of the Seleucid Empire. He was succeeded by his son Phraates I.

The Parthian Empire, also known as the Arsacid Empire, was a major Iranian political and cultural power centered in ancient Iran from 247 BC to 224 AD. Its latter name comes from its founder, Arsaces I, who led the Parni tribe in conquering the region of Parthia in Iran's northeast, then a satrapy (province) under Andragoras, who was rebelling against the Seleucid Empire. Mithridates I greatly expanded the empire by seizing Media and Mesopotamia from the Seleucids. At its height, the Parthian Empire stretched from the northern reaches of the Euphrates, in what is now central-eastern Turkey, to present-day Afghanistan and western Pakistan. The empire, located on the Silk Road trade route between the Roman Empire in the Mediterranean Basin and the Han dynasty of China, became a center of trade and commerce.