The Azerbaijanis[15][16] are an ethnic group mainly found in northwestern Iran and the Republic of Azerbaijan. Commonly referred to as Azeris (Azeri: آذریلر Azәrilәr) or Āzarīs (Persian: آذری ), they also live in a wider area from the Caucasus to the Iranian plateau. The Azeris are typically Muslim and have a mixed cultural heritage of Turkic, Iranian, and Caucasian elements.

Despite living on both sides of an international border, the Azeris form a single group. However, northerners and southerners differ due to nearly two centuries of separate social evolution in Russian/Soviet-influenced Azerbaijan and Iranian Azarbaijan. The Azerbaijani language unifies Azeris and is mutually intelligible with Turkmen and Turkish (including the dialects spoken by the Iraqi Turkmen and by the Qashqai). All of these languages are traced to the Turkic Oghuz, who moved into the Caucasus from Central Asia in the 11th century. Following the Russian-Persian Wars of the 18th and 19th centuries, territories controlled by Persia in the Caucasus (some merely under nominal control) were ceded to the Russian Empire. This included parts of the current Republic of Azerbaijan. The treaties of Golestan in 1813 and Turkmanchai in 1828 finalized the border between Russia and Persia (Iran).

As a result of this separate existence, the Azeris are mainly secularists in Azerbaijan and religious Muslims in Iranian Azarbaijan. Since Azerbaijan's independence from the Soviet Union in 1991, there has been renewed interest in religion and cross-border ethnic ties.