The Kapudan Pasha (Ottoman Turkish: قپودان پاشا, modern Turkish: Kaptan Paşa), was the Grand Admiral of the navy of the Ottoman Empire. He was also known as the Kapudan-ı Derya (Ottoman: قپودان دریا, modern: Kaptan-ı Derya, "Captain of the Sea"). Typically, he was based at Galata and Gallipoli during the winter and charged with annual sailings during the summer months. The title of Kapudan Pasha itself is only attested from 1567 onwards; earlier designations for the supreme commander of the fleet include Derya Bey ("bey of the sea") and Re'is Kapudan ("head captain").
The title Derya Bey was first granted during the reign of Bayezid I as an official rank within the state structure. Following the Conquest of Constantinople, Mehmet II raised Baltaoğlu Süleyman Bey to the status of sanjak bey for his efforts against the Byzantines in the Golden Horn. Baltaoğlu received the sanjak of Gallipoli (the principal Turkish naval base) and the kazas of Galata (until the Conquest a Genovese colony) and İzmit (whose tax remittance consisted of ship timber).
The success of Hayreddin Barbarossa saw the Kapudan Pasha elevated to the ranks of beylerbey and vizier in 1535, with his territories expanded into the Eyalet of the Archipelago and Algiers. Hayreddin's successors succeeded to these holdings, but saw their rank drop to two-horsetail vizier for several centuries.