The Ilkhanate, also spelled Il-khanate (Persian: ایلخانان, Ilxānān; Mongolian: Хүлэгийн улс, Hu’legīn Uls), was established as a khanate that formed the southwestern sector of the Mongol Empire, ruled by the Mongol House of Hulagu. It was founded in the 13th century and was based primarily in Iran as well as neighboring territories, such as present-day Azerbaijan and the central and eastern parts of present-day Turkey. The Ilkhanate was originally based on the campaigns of Genghis Khan in the Khwarazmian Empire in 1219–24 and was founded by Hulagu Khan, son of Tolui and grandson of Genghis Khan. With the fragmentation of the Mongol Empire after 1259 it became a functionally separate khanate. At its greatest extent, the state expanded into territories that today comprise most of Iran, Iraq, Armenia, Azerbaijan, Georgia, Turkmenistan, Turkey, western Afghanistan, and southwestern Pakistan. Later Ilkhanate rulers, beginning with Ghazan in 1295, would convert to Islam.
According to the historian Rashid-al-Din Hamadani, Kublai Khan granted Hulagu (Hülegü) the title of Ilkhan after his defeat of Ariq Böke. The term il-Khan means "subordinate khan" and refers to their initial deference to Möngke Khan and his successor Great Khans of the Mongol empire. The title "Ilkhan", borne by the descendants of Hulagu and later other Borjigin princes in Persia, does not materialize in the sources until after 1260.
When Muhammad II of Khwarezm executed a contingent of merchants dispatched by the Mongols, Genghis Khan declared war on the Khwārazm-Shāh dynasty in 1219. The Mongols overran the empire, occupying the major cities and population centers between 1219 and 1221. Persian Iran was ravaged by the Mongol detachment under Jebe and Subedei, who left the area in ruin. Transoxiana also came under Mongol control after the invasion. The undivided area west of the Transoxiana was the inheritance of Genghis Khan's Borjigin family. Thus, the families of the latter's four sons appointed their officials under the Great Khan's governors, Chin-Temür, Nussal, and Korguz, in that region.
Muhammad's son Jalal ad-Din Mingburnu returned to Iran in c. 1224 after his exile in India. The rival Turkic states, which were all that remained of his father's empire, quickly declared their allegiance to Jalal. He repulsed the first Mongol attempt to take Central Persia. However, Jalal ad-Din was overwhelmed and crushed by Chormaqan's army sent by the Great Khan Ögedei in 1231. During the Mongol expedition, Azerbaijan and the southern Persian dynasties in Fars and Kerman voluntarily submitted to the Mongols and agreed to pay tribute. To the west, Hamadan and the rest of Persia was secured by Chormaqan. The Mongols invaded Armenia and Georgia in 1234 or 1236, completing the conquest of the Kingdom of Georgia in 1238. They began to attack the western parts of Greater Armenia, which was under the Seljuks, the following year.
In 1236 Ögedei was commanded to raise up Khorassan and proceeded to populate Herat. The Mongol military governors mostly made camp in the Mughan plain in what is now Azerbaijan. Realizing the danger posed by the Mongols, the rulers of Mosul and Cilician Armenia submitted to the Great Khan. Chormaqan divided the Transcaucasia region into three districts based on the Mongol military hierarchy. In Georgia, the population was temporarily divided into eight tumens. By 1237 the Mongol Empire had subjugated most of Persia (including modern-day Azerbaijan), Armenia, Georgia (excluding Abbasid Iraq and Ismaili strongholds), as well as all of Afghanistan and Kashmir. After the battle of Köse Dağ in 1243, the Mongols under Baiju occupied Anatolia, while the Seljuk Sultanate of Rûm and the Empire of Trebizond became vassals of the Mongols. Güyük Khan abolished decrees issued by the Mongol princes that had ordered the raising of revenue from districts in Persia as well as offering tax exemptions to others in c. 1244.