Ghiyath al-Din Mahmud (Persian: غیاث الدین محمود), was Sultan of the Ghurid Empire from 1206 to 1212.

Ghiyath, not glad about Taj al-Din controlling Ghazni, and not daring to leave Ghur unprotected, requested help from the Khwarazmian Muhammad II of Khwarezm.

Husain ibn Kharmil, a former Ghurid general, who had changed allegiance to the Khwarazmians, shortly entered a negotiation with Ghiyath.

Thirteen months later, Muhammad was freed from captivity, and once again invaded the domains of Ghiyath, capturing Herat.

Ghiyath then agreed to recognize Muhammad's authority, and remained ruler of the Ghurid dynasty until he was assassinated in 1212.