The Church of Saint Demetrius, the saint protector of Thessaloniki, is one of the 15 Paleochristian and Byzantine Monuments of the city that were included in the UNESCO World Heritage List in 1988.

When the emperor made Christianity the official religion of the Byzantine Empire, people built a church on the place of the martyrdom of Agios Dimitrios, close to the Roman baths. His grave was said to be miraculous and thousands of travelers were coming every year to pay their honors.

Shortly afterward, the church was destroyed, but then then rebuilt. During the Turkish occupation, the church was converted into a mosque and in 1912, as the city was deliberated, it became a Christian church again. However, it started to function again in 1949.

Saint Demetrius became the patron saint of the city in 1912, during the First Balkan War, when the Greek army entered the city of Thessaloniki on his name day (October 26th) and delivered the city from the Turks. Today, his memory is celebrated every year with a big parade.