Imad ad-Din Zengi (Arabic: عماد الدین زنكي‎‎; Modern Turkish: İmadeddin Zengi; c. 1085 – 14 September 1146), also romanized as Zangi, Zengui, Zenki, and Zanki, was a Turkish atabeg who ruled Mosul, Aleppo, Hama, and Edessa. He was the namesake of the Zengid dynasty.

Zengi's father, Aq Sunqur al-Hajib, governor of Aleppo under Malik Shah I, was beheaded for treason in 1094, and Zengi was brought up by Kerbogha, the governor of Mosul.

Following the death in 1128 of Toghtekin, atabeg of Damascus, a power vacuum threatened to open Syria to renewed Crusader aggression. Zengi became atabeg of Mosul in 1127 and of Aleppo in 1128, uniting the two cities under his personal rule, and was formally invested as their ruler by the Sultan Mahmud II of Great Seljuk. Zengi had supported the young sultan against his rival, the caliph Al-Mustarshid.

In 1130 Zengi allied with Taj al-Mulk Buri of Damascus against the crusaders, but this was only a ruse to extend his power; he had Buri's son taken prisoner and seized Hama from him. Zengi also besieged Homs, the governor of which was accompanying him at the time, but could not capture it, so he returned to Mosul, where Buri's son and the other prisoners from Damascus were ransomed for 50,000 dinars. In 1131 Zengi agreed to return the 50,000 dinars if Buri would deliver to him Dubays ibn Sadaqa, emir of al-Hilla in Iraq, who had fled to Damascus to escape al-Mustarshid. When an ambassador from the caliph arrived to bring Dubais back, Zengi attacked him and killed some of his retinue; the ambassador returned to Baghdad without Dubais.

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