Andragoras (Seleucid satrap) in the context of "Antiochus I Soter"

The Parthian Empire (/ˈpɑːrθiən/), also known as the Arsacid Empire (/ˈɑːrsəsɪd/), 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 (r. c. 171 – 132 BC) 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.

The Parthians largely adopted the art, architecture, religious beliefs, and regalia of their culturally heterogeneous empire, which encompassed Persian, Hellenistic, and regional cultures. For about the first half of its existence, the Arsacid court adopted elements of Greek culture, though it eventually saw a gradual revival of Iranian traditions. The Arsacid rulers were titled "King of Kings", claiming inheritance of the Achaemenid Empire; indeed, they accepted many local kings as vassals, although the Achaemenids would have had centrally appointed, albeit largely autonomous, satraps. The court did appoint a small number of satraps, largely outside Iran, but these satrapies were smaller and less powerful than the Achaemenid potentates. With the expansion of Arsacid power, the seat of central government shifted from Nisa to Ctesiphon along the Tigris (south of Baghdad), although several other sites also served as capitals.

Arsaces I (/ˈɑːrsəsiːz/; from Ancient Greek: Ἀρσάκης; in Parthian: 𐭀𐭓𐭔𐭊‎, romanized: Aršak) was the first king of Parthia, ruling from 247 BC to 217 BC, as well as the founder and eponym of the Arsacid dynasty of Parthia. The leader of the Parni, one of the three tribes of the Dahae confederacy, Arsaces founded his dynasty in the mid-3rd century BC when he conquered the satrapy of Parthia (now shared between Turkmenistan and Iran) from Andragoras, who had rebelled against the Seleucid Empire. He spent the rest of his reign consolidating his rule in the region, and successfully stopped the Seleucid efforts to reconquer Parthia. Due to Arsaces' achievements, he became a popular figure amongst the Arsacid monarchs, who used his name as a royal honorific. By the time of his death, Arsaces had laid the foundations of a strong state, which would eventually transform into an empire under his great-grandnephew, Mithridates I, who assumed the ancient Near Eastern royal title of King of Kings. Arsaces was succeeded by his son Arsaces II.

Literary sources are very scarce on Arsaces, and exclusively come from contradictory Greek and Roman accounts written centuries after his death. As a result, his reign is sparsely known. His existence was even questioned by modern scholars, until new studies and archaeological findings confirmed his identity in the 1960s.

In 245 BC, Andragoras, the Seleucid governor (satrap) of Parthia ("roughly western Khurasan") proclaimed independence from the Seleucids, when - following the death of Antiochus II - Ptolemy III seized control of the Seleucid capital at Antioch, and "so left the future of the Seleucid dynasty for a moment in question."

Meanwhile, "a man called Arsaces, of Scythian or Bactrian origin, [was] elected leader of the Parni tribes." Following the secession of Parthia from the Seleucid Empire and the resultant loss of Seleucid military support, Andragoras had difficulty in maintaining his borders, and about 238 BCE—under the command of "Arsaces and his brother Tiridates"—the Parni invaded Parthia and seized control of Astabene (Astawa), the northern region of that territory, the administrative capital of which was Kabuchan (Kuchan in the vulgate).

The Parthian Empire (/ˈpɑːrθiən/), also known as the Arsacid Empire (/ˈɑːrsəsɪd/), 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 (r. c. 171 – 132 BC) 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.

The Parthians largely adopted the art, architecture, religious beliefs, and regalia of their culturally heterogeneous empire, which encompassed Persian, Hellenistic, and regional cultures. The Arsacid court initially adopted elements of Greek culture, though it eventually saw a gradual revival of Iranian cultural traditions. In modern historiography, the Arsacids are considered the first indigenous Iranian dynasty to come to power in the Iranian world after the Achaemenids, in contrast to the Seleucids who represented Hellenistic rule after Alexander the Great. The Arsacid rulers were titled "King of Kings", claiming the inheritance of the Achaemenid Empire; indeed, they accepted many local kings as vassals, though the Achaemenids had centrally appointed, albeit largely autonomous, satraps. The Parthian court appointed a small number of satraps, largely outside Iran, but these satrapies were smaller and less powerful than the Achaemenid potentates. With the expansion of Arsacid power, the seat of central government shifted from Nisa to Ctesiphon along the Tigris (south of Baghdad), although several other sites also served as capitals.