The Karluks (also Qarluqs, Qarluks, Karluqs, 𐰴𐰺𐰞𐰸, Qarluq, Para-Mongol: Harluut, Géluólù ; customary phonetic: Gelu, Khololo, Khorlo, خَلُّخ, Khallokh, قارلوق Qarluq) were a prominent nomadic Turkic tribal confederacy residing in the regions of Kara-Irtysh (Black Irtysh) and the Tarbagatai Mountains west of the Altay Mountains in Central Asia. Karluks gave their name to the distinct Karluk group of the Turkic languages, which also includes the Uzbek, Uyghur and Ili Turki languages.
Karluks were known as a coherent ethnic group with autonomous status within the Göktürk khaganate and the independent states of the Karluk yabghu, Karakhanids and Qarlughids before being absorbed in the Chagatai Khanate of the Mongol empire.
They were also called Uch-Oghuz meaning "Three Oghuz". Despite the similarity of names, Mahmud al-Kashgari's Dīwān Lughāt al-Turk wrote: "Karluks is a division of nomadic Turks. They are separate from Oghuz, but they are Turkmens like Oghuz.". Ilhanate's Rashid-al-Din Hamadani in his Jami' al-tawarikh mentions Karluks as one of the Oghuz (Turkmen) tribes. Kafesoğlu (1958) proposes that Türkmen might be the Karluks' equivalent of the Göktürks' political term Kök Türk.
Nikolai Aristov noted that a tributary of the Charysh River was Kerlyk and proposed that the tribal name originated from the toponym with a Turkic meaning of "wild Siberian millet".
Peter Golden, citing Németh, suggests that qarluğ/qarluq possibly means "snowy" (from Proto-Turkic *qar "snow"). However, Marcel Erdal critiques this as a folk etymology, as "[i]n Old Turkic the suffix +lXk, which is implied in this account, had fourfold vowel harmony, and the +lXk derivate from kar would in Old Turkic be *karlık and not karluk".
Having noted that the majority of Chinese transcriptions 歌邏祿, 歌羅祿, 葛邏祿, 葛羅祿 and 哥邏祿 (all romanized as Geluolu) are trisyllabic, while only one form 葛祿 (Gelu) is disyllabic, Erdal contends that although the latter one transcribed Qarluq, the former four transcribed *Qaraluq, which should be the preferred reading.