The Basilica of St. John is an ancient basilica located in Selcuk, Turkey, near the ancient city of Ephesus. It was constructed in the 6th century AD by Emperor Justinian I on the site where St. John the Apostle is believed to have been buried. The basilica was an important pilgrimage site in the Byzantine period and was one of the largest churches in the region.

The basilica was built in the shape of a cross and had a dome at the center. It was decorated with intricate mosaics and frescoes, many of which can still be seen today. The church was destroyed by earthquakes in the 7th century and was subsequently abandoned.

The ruins of the basilica were rediscovered in the late 19th century and have since been partially restored. Today, visitors can explore the ruins of the basilica and see the remains of the original structure, including the columns, arches, and decorative elements. The site also offers stunning views of the surrounding landscape, including the nearby town of Selcuk and the ancient city of Ephesus.