The Fethiye Mosque (Greek: Φετιχιέ τζαμί; Turkish: Fethiye Camii, "Mosque of the Conquest") is a 17th-century Ottoman mosque in central Athens, Greece. The Fethiye Mosque is located on the northern side of the ancient Roman Agora in Athens, near the Tower Of The Winds, and was built on the ruins of a Christian basilica from the middle Byzantine period (8th/9th centuries). The Christian church was converted into a mosque in 1456/58, soon after the Ottoman conquest of the Duchy of Athens, to coincide with the visit to the city by Sultan Mehmed the Conqueror in 1458.
Only a fragment of the mihrab survives from this mosque, which was demolished and replaced by the present structure between 1668 and 1670. The new mosque comprises a porch and a large rectangular main hall, crowned by a dome supported by four pillars. The central dome is flanked by half-domes on each side, and by smaller domes on each corner.
The porch is supported by five arches, each crowned by a small dome, resting on masonry on the sides and four pillars in the middle. During Ottoman times, it was commonly known as the "Wheatmarket Mosque" (Τζαμί του Σταροπάζαρου). During the brief occupation of the city by the Venetian forces in the Morean War (October 1687 – May 1688), the mosque was converted by the Venetians into a Catholic church, dedicated to Dionysius the Areopagite.