Pahlavi is a term that refers: (1) to a script used in Iran derived from the Aramaic script, and (2) more broadly, to Middle Persian, the Middle Iranian language written in this script. The Pahlavi script was used broadly in the Sasanid Persian Empire to write down Middle Persian for secular, as well as religious purposes.

One unique feature of Pahlavi orthography is the use of Aramaic "masks" to render many common Pahlavi words. For example, the Pahlavi word for "king", shah, was written as MLKA, recognizable as the Aramaic word for "king" cognate with contemporary Arabic malik, but intended to be pronounced as shah. Masking was also applied to verbs, where Pahlavi person-number agreement and tense markers were appended to an Aramaic third-person masculine singular verb. Many extremely common nouns, verbs, and even function words were subject to masking.

The modern-day descendent of Middle Persian is Modern Persian. The latter is distinguished from the former by, among other things, being written in a different script, the Perso-Arabic script, and by a large number of Arabic loanwords. Pahlavi Middle Persian is the language of quite a large body of Zoroastrian literature which details the traditions and prescriptions of the Zoroastrian religion which was the state religion of Sassanid Iran (224 to ca. 650) before Iran was defeated by the Arab armies that introduced Islam.

The Middle Persian language was also written down in the Manichean script by followers of that religion.

See also: Pahlavi Literature