The Basilica of St. John was a basilica in Ephesus. It was constructed by Justinian I in the 6th century. It stands over the believed burial site of John the Apostle. It was modelled after the now lost Church of the Holy Apostles in Constantinople.

The basilica is on the slopes of Ayasuluk Hill, right next to the İsa Bey Mosque, just below the fortress near the centre of Selçuk, İzmir Province, Turkey and about 3.5 km (2.2 mi) from Ephesus.