The Parthian Empire (/ˈpɑːrθiən/; 247 BC – 224 AD), also known as the Arsacid Empire (/ˈɑːrsəsɪd/),[9] was a major Iranian political and cultural power in ancient Iran.[10] Its latter name comes from Arsaces I of Parthia[11] who, as leader of the Parni tribe, founded it in the mid-3rd century BC when he conquered the region of Parthia[12] in Iran's northeast, then a satrapy (province) under Andragoras, in rebellion against the Seleucid Empire. Mithridates I of Parthia (r. c. 171–138 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 eastern Iran. 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 royal insignia 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 the "King of Kings", as a claim to be the heirs to the Achaemenid Empire; indeed, they accepted many local kings as vassals where 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 modern Baghdad, Iraq), although several other sites also served as capitals.

The earliest enemies of the Parthians were the Seleucids in the west and the Scythians in the north. However, as Parthia expanded westward, they came into conflict with the Kingdom of Armenia, and eventually the late Roman Republic. Rome and Parthia competed with each other to establish the kings of Armenia as their subordinate clients. The Parthians soundly defeated Marcus Licinius Crassus at the Battle of Carrhae in 53 BC, and in 40–39 BC, Parthian forces captured the whole of the Levant except Tyre from the Romans. However, Mark Antony led a counterattack against Parthia, although his successes were generally achieved in his absence, under the leadership of his lieutenant Ventidius. Various Roman emperors or their appointed generals invaded Mesopotamia in the course of the ensuing Roman–Parthian Wars of the next few centuries. The Romans captured the cities of Seleucia and Ctesiphon on multiple occasions during these conflicts, but were never able to hold on to them. Frequent civil wars between Parthian contenders to the throne proved more dangerous to the Empire's stability than foreign invasion, and Parthian power evaporated when Ardashir I, ruler of Istakhr in Persis, revolted against the Arsacids and killed their last ruler, Artabanus IV, in 224 AD. Ardashir established the Sassanid Empire, which ruled Iran and much of the Near East until the Muslim conquests of the 7th century AD, although the Arsacid dynasty lived on through the Arsacid Dynasty of Armenia, the Arsacid dynasty of Iberia, and the Arsacid Dynasty of Caucasian Albania; all eponymous branches of the Parthian Arsacids.

Native Parthian sources, written in Parthian, Greek and other languages, are scarce when compared to Sassanid and even earlier Achaemenid sources. Aside from scattered cuneiform tablets, fragmentary ostraca, rock inscriptions, drachma coins, and the chance survival of some parchment documents, much of Parthian history is only known through external sources. These include mainly Greek and Roman histories, but also Chinese histories, prompted by the Han Chinese desire to form alliances against the Xiongnu.[13] Parthian artwork is viewed by historians as a valid source for understanding aspects of society and culture that are otherwise absent in textual sources.