Grand vizier (Persian: وزيرِ اعظم, romanized: vazîr-i aʾzam; Ottoman Turkish: صدر اعظم, romanized: sadr-ı aʾzam; Turkish: sadrazam) was the title of the effective head of government of many sovereign states in the Islamic world. The office of Grand Vizier has its origin in the Wuzurg Framadār, the highest ranking official of the Sasanian state. After Islam, it was first held by officials in the later Abbasid Caliphate. It was then held in the Ottoman Empire, the Mughal Empire, the Sokoto Caliphate the Safavid Empire and Morocco. In the Ottoman Empire, the Grand Vizier held the imperial seal and could convene all other viziers to attend to affairs of the state; the viziers in conference were called "Kubbealtı viziers" in reference to their meeting place, the Kubbealtı ('under the dome') in Topkapı Palace. His offices were located at the Sublime Porte. Today, the Prime Minister of Pakistan is referred to in Urdu as Wazir-e-azam, which translates literally to Grand Vizier.

Initially, the Grand Viziers were exclusively of Turk origin in the Ottoman Empire. However, after there were troubles between the Turkish Grand Vizier Çandarlı Halil Pasha the Younger and Sultan Mehmed II (who had him executed), there was a rise of slave administrators (devshirme). These were much easier for the sultans to control, as compared to the free administrators of Turkish aristocratic origin.