The Qajars (Persian: ایل قاجار, romanized: Il-e Ǧâjâr; Azerbaijani: قاجارلار, romanized: Qacarlar) are a clan of the Bayat tribe of the Oghuz Turks. While linguistically and culturally Turkic, the Qajars are genetically distinct as an indigenous Caucasian group that underwent Turkification during the early migrations into the region. The tribe lived in the area that is now Armenia, Azerbaijan and Northwestern Iran.

By the end of the Safavid era, the Qajars had split into several factions. These included the Ziyādoghlu (Ziādlu), associated with the area of Ganja and Yerevan, as well as the Qoyunlu (Qāvānlu), and Davālu (Devehlu) the latter two associated with the northern areas of contemporary Iran. In 1796, Agha Mohammad Khan, a Qajar chief of the Qoyunlu branch, was crowned Shah of Iran, founding the Qajar dynasty, which ruled Iran until 1925.

While traditionally categorized by their Turkic language, recent genetic research into the Qajars' paternal lineage, specifically the identification of Haplogroup J-M267, suggests a paternal origin indigenous to the Caucasus and West Asia. This indicates that the tribe's core lineage likely emerged from an autochthonous Caucasian population that underwent Turkification through linguistic and cultural assimilation during the Oghuz migrations into the Iranian plateau, rather than originating from the Central Asian or Siberian gene pools associated with early Turkic groups.

The Qajars were one of the original Turkoman Qizilbash tribes. They later supplied power to the Safavids since this dynasty's earliest days. Numerous members of the Qajar tribe held prominent ranks in the Safavid state. In 1794, a Qajar chieftain, Agha Mohammad Khan, a member of the Qoyunlu branch of the Qajars, founded the Qajar dynasty which replaced the Zand dynasty in Iran. He launched his campaign from his power base south of the Caspian Sea, capturing its capital Isfahan in 1785. A year later, Tehran accepted Agha Mohammad's authority.

According to An Ethnohistorical Dictionary of the Russian and Soviet Empires by Olson et al., which was published in 1994 and specifically deals with the ethnography of the Russian Empire and Soviet Union, the Qajars were historically a Turkic tribe that lived in Armenia. They resettled in the region of Azerbaijan during the 17th and 18th centuries. Olson considers them to be a tribal subgroup of Iranian Azerbaijanis. American anthropologist Richard Weeks also notes that the Azerbaijanis of Iran, depending on their place of residence, use the designation Qajar.

Olson et al. add that in the 1980s the Qajar population exceeded 35,000 people, most of whom lived in Iran.

According to Faruk Sümer, the Ağca Koyunlu tribe was one of the four branches forming the Qajars. In the Ottoman tribal registers, the Ağca Koyunlu tribe, shown as a nomadic (hayme-nişin) Turkmen Yörük tribe, is seen to have spread over a wide geography including Aleppo, Zile, Sivas, Adana, Gönen, Kula, Bursa, Kayseri, Maraş, Konya, Karaman, Mihaliç and Tarsus. Located in the Eski Kaçerli (Old Kaçerli) neighborhood of Emirdağ, a mosque is named after the Qajars. In this regard, in a decree sent by Ottoman sultan Ahmed III to the Beylerbey of Rakka stated that the tribes from the Muslucalu community of Bozulus Turkmens, including the Qajars, were settled in today's Emirdağ.