THE Thessaloniki it is the second most populous city in Greece. It is the seat of the municipality of the same name, the Regional Unit of Thessaloniki, the Region of Central Macedonia and the Decentralized Administration of Macedonia Thrace. From its founding by Kassandros, Thessaloniki as a flourishing Hellenistic city until the Ottoman rule took advantage of its strategic position and developed into a multicultural city. Since 1912, with the end of the Balkan wars and the integration of the region into the modern Greek State, Thessaloniki has been the second most populous city in Greece.

The population of the urban complex is currently estimated at 1,110,312 inhabitants (2011).

The foundation of the city in the Hellenistic era coincides with a critical phase in the history of the Macedonian Kingdom, which begins with the early death of Alexander the Great and with the claim to the Macedonian king's throne by his descendants. In order to be able to claim the throne of Macedonia, the general Kassandros married the half-sister of Alexander the Great, Thessaloniki, in whose honor he founded the city by uniting 26 polykhnes, which were located around the Thermaic gulf.

In the 2nd BC century the city was conquered by the Romans, like the rest of Greece and became the seat of the Roman subject of Macedonia. The strategic position of the city is evident in principle, when it was chosen as the Imperial capital during the reign of Galerius, when the imperial palace was built.

Its importance was also shown later by the intention of the transfer of the capital of the Roman Empire by Constantine the Great to the east, as it was one of the candidate cities that had been proposed as replacements for Rome, so that Byzantium was finally chosen. Despite not being chosen as the capital, it gets its title Co-regent city and during the Byzantine period.

After its conquest by the Ottomans in 1432, it remained in the Ottoman Empire for about five centuries. With the expulsion of the Jews from the Iberian peninsula, and Northern Europe, Thessaloniki acquires its own Jewish community.

This establishment of the Jews in Thessaloniki, highlighted the city as the most important world Jewish metropolis until at least the beginning of the 20th century. Especially since the middle of the 19th century, the city has been the most cosmopolitan urbanizing center of the Ottoman Empire and the most important pole of political movements and movements encountered in its long history.

With its inclusion in the body of the Greek State in 1912, the population of the city shows significant changes with the movement of the Muslim population and its replacement by refugee populations from Asia Minor and Eastern Thrace.

Population changes contributed to the change in the city's population situation with the strengthening of the Greek element. Its urban planning and architectural reorganization was accelerated by the Great Fire of 1917 and the efforts of the new Greek administration to add ancient Greek and European elements to the city's architectural style, which led to the destruction of several Ottoman religious and functional buildings.

The most important population changes are observed with the holocaust of the prosperous Jewish community by the Nazi troops during the period of the triple occupation during the Second World War, with the settlement of the Asia Minor and Thracian refugee population after the Asia Minor disaster in 1922 and with the internal migration that observed during the 50s and later towards the large urban centers.