Persian (Persian: ' fɒːɾˈsiː) is an Iranian language within the Indo-Iranian branch of the Indo-European languages. It is primarily spoken in Iran and known by Persian speakers as Farsi or Parsi, Afghanistan (officially known as "Dari Persian" since 1958 for political reasons), Tajikistan (officially known as "Tajik" since the Soviet era), and other countries which historically came under Persian influence. The Persian language is classified as a continuation of Middle Persian, the official religious and literary language of Sassanid Persia, itself a continuation of Old Persian, the language of the Persian Empire in the Achaemenid era. Persian is a pluricentric language and its grammar is similar to that of many contemporary European languages.

There are approximately 110 million Persian speakers worldwide, with the language holding official status in Iran, Afghanistan and Tajikistan. For centuries Persian has also been a prestigious cultural language in Central Asia, South Asia, and Western Asia. Persian is used as a liturgical language of Islam in Iran, Afghanistan, and Tajikistan.

Persian has had a considerable, mainly lexical influence on neighboring languages, particularly the Turkic languages in Central Asia, Caucasus, and Anatolia, neighboring Iranian languages, as well as Armenian, and Indo-Aryan languages, especially Urdu. It also exerted some influence on Arabic, particularly Iraqi Arabic and Khuzestani Arabic, while borrowing much vocabulary from it after the Muslim conquest of Persia.

With a long history of literature in the form of Middle Persian before Islam, Persian was the first language in Muslim civilization to break through Arabic’s monopoly on writing, and the writing of poetry in Persian was established as a court tradition in many eastern courts. Some of the famous works of Persian literature are the Shahnameh of Ferdowsi, works of Rumi, Rubaiyat of Omar Khayyam, Divan of Hafiz and poems of Saadi.