Parthia (𐎱𐎼𐎰𐎺 Parθava; 𐭐𐭓𐭕𐭅 Parθaw; 𐭯𐭫𐭮𐭥𐭡𐭥 Pahlaw) is a historical region located in northeastern Greater Iran. It was conquered and subjugated by the empire of the Medes during the 7th century BC, was incorporated into the subsequent Achaemenid Empire under Cyrus the Great in the 6th century BC, and formed part of the Hellenistic Seleucid Empire after the 4th-century BC conquests of Alexander the Great. The region later served as the political and cultural base of the Eastern Iranian Parni people and Arsacid dynasty, rulers of the Parthian Empire (247 BC – 224 AD). The Sasanian Empire, the last state of pre-Islamic Iran, also held the region and maintained the seven Parthian clans as part of their feudal aristocracy.
The name "Parthia" is a continuation from Latin Parthia, from Old Persian Parthava, which was the Parthian language self-designator signifying "of the Parthians" who were an Iranian people. In context to its Hellenistic period, Parthia also appears as Parthyaea.
Parthia was known as Pahlaw in the Middle Persian sources of the Sasanian period, and Pahla or Fahla by later Islamic authors, but mainly referred to the Parthian region in the West of Iran.
The original location of Parthia roughly corresponds to a region in northeastern Iran, but part is in southern Turkmenistan. It was bordered by the Kopet Dag mountain range in the north, and the Dasht-e-Kavir desert in the south. It bordered Media on the west, Hyrcania on the north west, Margiana on the northeast, and Aria on the east.
During Arsacid times, Parthia was united with Hyrcania as one administrative unit, and that region is therefore often (subject to context) considered a part of Parthia proper.
By the early Sasanian period, Parthia was located in the central part of the Iranian plateau, neighboring Pars to the south, Khuzistan to the south-west, Media to the north-west, the Alborz Mountains to the north, Abarshahr to the north-east, and Kirman to the east. In the late Sasanian era, Parthia came to embrace central and north-central Iran but also extended to the western parts of the plateau as well.