Thessaloniki (; Greek: Θεσσαλονίκη [θesaloˈnici] ; also known by various spellings and names) is the capital and largest city of the administrative region of Central Macedonia, and the second-largest city in Greece. It is the largest city of Northern Greece, with over 300,000 in the city proper and slightly over one million inhabitants in its metropolitan area, the capital of the geographic region of Macedonia, and the Decentralized Administration of Macedonia and Thrace. It is also known in Greek as i Symprotévousa (η Συμπρωτεύουσα), literally "the co-capital", a reference to its historical status as the "co-reigning" city (Symvasilévousa/Συμβασιλεύουσα) of the Byzantine Empire alongside Constantinople.
Thessaloniki is located on the Thermaic Gulf, at the northwest corner of the Aegean Sea. It is bounded on the west by the delta of the Axios. The municipality of Thessaloniki, the historical centre, had a population of 319,045 in 2021, while the Thessaloniki metropolitan area had 1,006,112 inhabitants and the greater region had 1,092,919. It is Greece's second major economic, industrial, commercial and political centre, and a major transportation hub for Greece and southeastern Europe, notably through the Port of Thessaloniki. The city is renowned for its festivals, events and vibrant cultural life in general. Events such as the Thessaloniki International Fair and the Thessaloniki International Film Festival are held annually. Thessaloniki was the 2014 European Youth Capital. The city's main university, Aristotle University, is the largest in Greece and the Balkans.
The city was founded in 315 BC by Cassander of Macedon, who named it after his wife Thessalonike, daughter of Philip II of Macedon and sister of Alexander the Great. It was built 40 km southeast of Pella, the capital of the Kingdom of Macedonia. An important metropolis by the Roman period, Thessaloniki was the second largest and wealthiest city of the Byzantine Empire. It was conquered by the Ottomans in 1430 and remained an important seaport and multi-ethnic metropolis during the nearly five centuries of Turkish rule, with churches, mosques, and synagogues co-existing side by side. From the 16th to the 20th centuries, it was the only Jewish-majority city in Europe. It passed from the Ottoman Empire to the Kingdom of Greece on 8 November 1912. Thessaloniki exhibits Byzantine architecture, including numerous Paleochristian and Byzantine monuments, a World Heritage Site, and several Roman, Ottoman and Sephardic Jewish structures.
In 2013, National Geographic Magazine included Thessaloniki in its top tourist destinations worldwide, while in 2014 Financial Times FDI magazine (Foreign Direct Investments) declared Thessaloniki as the best mid-sized European city of the future for human capital and lifestyle.
The original name of the city was Θεσσαλονίκη Thessaloníkē. It was named after the princess Thessalonike of Macedon, the half-sister of Alexander the Great, whose name means "Thessalian victory", from Θεσσαλός Thessalos, and Νίκη 'victory' (Nike), honoring the Macedonian victory at the Battle of Crocus Field (353/352 BC). A popular Greek legend has it that Thessalonike became a mermaid who lived in the Aegean after the death of Alexander the Great.
Minor variants are also found, including Θετταλονίκη Thettaloníkē, Θεσσαλονίκεια Thessaloníkeia, Θεσσαλονείκη Thessaloneíkē, and Θεσσαλονικέων Thessalonikéon.
The name Σαλονίκη Saloníki is first attested in Greek in the Chronicle of the Morea (14th century), and is common in folk songs, but it must have originated earlier, as al-Idrisi called it Salunik already in the 12th century. It is the basis for the city's name in other languages: Солѹнъ (Solunŭ) in Old Church Slavonic, סאלוניקו (Saloniko) in Judeo-Spanish (שאלוניקי prior to the 19th century) סלוניקי (Saloniki) in Hebrew, Selanik in Albanian, سلانیك (Selânik) in Ottoman Turkish and Selanik in modern Turkish, Salonicco in Italian, Solun or Солун in the local and neighboring South Slavic languages, Салоники (Saloníki) in Russian, Sãrunã in Aromanian and Săruna in Megleno-Romanian.
In English, the city can be called Thessaloniki, Salonika, Thessalonica, Salonica, Thessalonika, Saloniki, Thessalonike, or Thessalonice. In printed texts, the most common name and spelling until the early 20th century was Thessalonica (), matching the Latin name; through most of rest of the 20th century, it was Salonika (). By about 1985, the most common single name became Thessaloniki. The forms with the Latin ending -a taken together remain more common than those with the phonetic Greek ending -i and much more common than the ancient transliteration -e.
Thessaloniki was revived as the city's official name in 1912, when it joined the Kingdom of Greece during the Balkan Wars. In local speech, the city's name is typically pronounced with a dark and deep L, characteristic of the accent of the modern Macedonian dialect of Greek. The name is often abbreviated as Θεσ/νίκη.
From classical antiquity to the Roman Empire
The city was founded around 315 BC by the King Cassander of Macedon, on or near the site of the ancient town of Therma and 26 other local villages. He named it after his wife Thessalonike, a half-sister of Alexander the Great and princess of Macedonia as daughter of Philip II. Under the kingdom of Macedonia, the city retained its own autonomy and parliament and evolved to become the most important city in Macedonia. Nonetheless, Pella remained the capital of Macedon until its fall.
In 128 BC, twenty years after the fall of the Kingdom of Macedonia, Thessalonica was made the capital of the Roman province of Macedonia. Thessalonica became a free city of the Roman Republic under Mark Antony in 41 BC. It grew to be an important trade hub located on the Via Egnatia, the road connecting Dyrrhachium with Byzantium, which facilitated trade between Thessaloniki and great centres of commerce such as Rome and Byzantium. Thessaloniki also lies at the southern end of the main north–south route through the Balkans along the valleys of the Morava and Axios river valleys, thereby linking the Balkans with the rest of Greece. The city became the capital of one of the four Roman districts of Macedonia.
At the time of the Roman Empire, about 50 AD, Thessaloniki was also one of the early centres of Christianity; while on his second missionary journey, Paul the Apostle visited this city's chief synagogue on three Sabbaths and sowed the seeds for Thessaloniki's first Christian church. Later, Paul wrote letters to the new church at Thessaloniki, with two letters to the church under his name appearing in the Biblical canon as First and Second Thessalonians. Some scholars hold that the First Epistle to the Thessalonians is the first written book of the New Testament.
In 306 AD, Thessaloniki acquired a patron saint, St. Demetrius, a Christian whom Galerius is said to have put to death. Most scholars agree with Hippolyte Delehaye's theory that Demetrius was not a Thessaloniki native, but his veneration was transferred to Thessaloniki when it replaced Sirmium as the main military base in the Balkans. A basilical church dedicated to St. Demetrius, Hagios Demetrios, was first built in the fifth century AD and is now a UNESCO World Heritage Site.
When the Roman Empire was divided into the tetrarchy, Thessaloniki became the administrative capital of one of the four portions of the Empire under Galerius Maximianus Caesar, where Galerius commissioned an imperial palace, a new hippodrome, a triumphal arch and a mausoleum, among other structures.
Thessaloniki remained the administrative center of the Diocese of Macedonia. In 379, when the Roman Prefecture of Illyricum was divided between the East and West Roman Empires, Thessaloniki became the capital of the new Prefecture of Illyricum. The following year, the Edict of Thessalonica made Christianity the state religion of the Roman Empire. In 390, troops under the Roman Emperor Theodosius I led a massacre against the inhabitants of Thessalonica, who had risen in revolt against the detention of a favorite charioteer. By the time of the Fall of Rome in 476, Thessaloniki was the second-largest city of the Eastern Roman Empire.