The Parthian language, also known as Arsacid Pahlavi and Pahlawānīg, is an extinct ancient Northwestern Iranian language once spoken in Parthia, a region situated in present-day northeastern Iran and Turkmenistan. Parthian was the language of state of the Arsacid Parthian Empire (248 BC – 224 AD), as well as of its eponymous branches of the Arsacid dynasty of Armenia, Arsacid dynasty of Iberia, and the Arsacid dynasty of Caucasian Albania.

Parthian had a significant impact on Armenian, a large part of whose vocabulary was formed primarily from borrowings from Parthian, and had a derivational morphology and syntax that was also affected by language contact but to a lesser extent. Many ancient Parthian words were preserved and now survive only in Armenian. The Semnani or Komisenian languages may descend from Parthian directly or be a Caspian language with Parthian influences, but the topic lacks sufficient research.