The İsa Bey Mosque (Turkish İsa Bey Camii) is located in Selçuk at the southwestern foot of Ayasoluk Castle Hill below the Citadel and St. John's Basilica. It encloses an area of about 56.5 × 48.5 m and consists of an arcade courtyard and a three-part prayer room.

Through the western main portal, which is surrounded by a serrated border, is bricked alternately with yellowish and white stones and is closed off at the top by a muqarnas, one enters the inner courtyard, of whose arcades only individual columns can be seen on three sides. Above the portal stands the only remaining minaret, the second was above the opposite mountain gate. A third, smaller gate is on the north side.

Sultan İsa Bey I. (1360-1390), son of Mehmet Bey, the founder of the Seljuk dynasty of the Aydinogullari, who ruled Western Anatolia in the 14th and 15th centuries, had the mosque built by Damascus architect Ali ibn el Dimiski in the style of an Arab court mosque in 777 of the Islamic calendar (1374 AD) according to the building inscription above the main portal.

The partially preserved minaret

The arcades of the inner courtyard were destroyed during the earthquakes of 1653 and 1668. One of the two minarets on the northeast and northwest corners of the prayer room was completely destroyed, the other was removed to the balcony.

In the centre of the courtyard there is an octagonal fountain.

The door with three ogival passages on the south side leads into the actual three-part prayer room of about 18 × 48 m. The central part with pulpit and mihrab (prayer niche) is crowned by two Ottoman domes, which are decorated inside with turquoise and blue faiences. The four vaulted dark granite columns originate from the harbour baths of Ephesos.

After the building had been used for a long time as a caravanserai, the mosque was reopened in 1975 after a complete restoration. In 2005 a renovation was carried out, during which, among other things, the lead roof was renewed.