The Zeynep Sultan Mosque (in Turkish Zeynep Sultan Camii) is a mosque built in 1769 by Ayazma Mosque's architect Mehmet Tahir Ağa for Ahmed III's daughter Zeynep Sultan. It evokes Byzantine churches because of its architectural style and materials that were used in its construction.
The mosque is on Alemdar Caddesi (Street) in Istanbul, across the street from Gülhane Park, not far from the Hagia Sophia, and visible from the tram that circulates the city. In the back side of the mosque, there is a building, which was once used as mektep and now being used as primary school. The part once used as sebil is now closed. In front of the mosque, there is a fountain, which was actually part of Abdul-Hamid I's külliye. The fountain was carried here in 1920s when 4. Vakıf Han's construction in Eminönü. The "Osmanlı Araştırmaları Vakfı" (English: Foundation for Research on the Ottoman Empire is above the mosque.