Komotini (Greek: Κομοτηνή, Turkish: Gümülcine, Bulgarian: Гюмюрджина, romanized: Gyumyurdzhina), is a city in the region of East Macedonia and Thrace, northeastern Greece and its capital. It is also the capital of the Rhodope. It was the administrative centre of the Rhodope-Evros super-prefecture until its abolition in 2010, by the Kallikratis Plan. The city is home to the Democritus University of Thrace, founded in 1973. Komotini is home to a sizeable Muslim minority, which was exempted from the population exchange between Greece and Turkey. According to the 2021 census, the municipality of Komotini had a population of 65,243 citizens.

Built at the northern part of the plain bearing the same name, Komotini is one of the main administrative, financial and cultural centers of northeastern Greece and also a major agricultural and breeding center of the area. It is also a significant transport interchange, located 795 km NE of Athens and 281 km NE of Thessaloniki. The presence of the Democritus University of Thrace makes Komotini the home of thousands of Greek and international students and this, combined with an eclectic mix of Western and Oriental elements in the city's daily life, have made it an increasingly attractive tourist destination.

Komotini has existed as a settlement since the 2nd century AD. That is confirmed by archaeological finds of that era up until the 4th century. It is also confirmed by an inscription on the ruins of the 4th-century Byzantine wall, that are visible at various sites in the city, which reads "Theodosiou Ktisma" = Building of Theodosius. The inscription was discovered by the Komotini-born Prof. Stilponas Kyriakidis and the then mayor Sofoklis Komninos. It is said that the settlement originates from the 5th century and is linked to the daughter of the painter Parrasios from Maroneia. During the Roman age it was one of several fortresses along the Via Egnatia highway which existed in the Thrace area. Probably it is to be identified with the Roman station Breierophara (a Thracian toponym from bre (=fortress) + iero (= holy) + phara=para (=pass). The most important city of that period was neighbouring Maximianopolis, former Thracian Porsulis or Paesoulae, which was renamed to Mosynopolis in the 9th century. Komotini was a Via Egnatia hub on its northern route through the Nymphaea Pass which led to the Ardas Valley, Philippopolis (modern Plovdiv) and Byzantine Berroe (modern Stara Zagora).

The city's history is closely connected with that of Via Egnatia, the Roman trunk road which connected Dyrrhachium with Constantinople. The Roman emperor Theodosius I built a small rectilinear fortress on the road at a junction with a route leading north across the Rhodope Mountains toward Philippopolis. During the Byzantine period, the city belonged to the Theme of Macedonia, whilst from the 11th century it could be found within the newly founded theme of Boleron. For most of its early existence the settlement was overshadowed by the larger town of Mosynopolis to the west, and by the end of the 12th century, the place had been completely abandoned.

The current settlement dates to 1207, when, following the destruction of Mosynopolis by the Bulgarian tsar Kaloyan, the remnant population fled and established themselves within the walls of the abandoned fortress. Since then the population had been increasing continuously until it became an important town within the area. In 1331 John Kantakouzenos referred to her as Koumoutzina in his account of the Byzantine civil war of 1321–1328. In 1332 Andronikos III Palaiologos set camp in Komotini to face Umur Bey of Smyrna at the Panagia village close to the Panagia Vathirryakos (Fatirgiaka) monastery. However, Umur departed without a battle. In 1341 the historian Nikephoros Phokas referred to the town with its current name. In 1343, during the civil war between John VI Kantakouzenos and John V Palaiologos, Komotini along with the neighbouring forts of Asomatos, Paradimi, Kranovouni and Stylario joined Kantakouzenos' side. John VI Kantakouzenos escaped to Komotini to survive from a battle with the army of the Bulgarian brigand Momchil near the already ruined Mosynopolis.

The city was conquered by the Ottoman Empire between 1361 and 1362/3, apparently by Gazi Evrenos Bey. Its conquest is placed after the fall of Philippopolis and Stara Zagora, but before the Ottoman capture of Pegae. Already before that, it was called in Turkish as Gümülcine, a version of the demotic Greek form of the city's name, Koumoutsinas. This remained the city's name throughout the Ottoman period (ca. 1361–1912) and continues as its modern Turkish-language name today.

The city continued to be an important hub connecting the capital city of Constantinople with the European part of the Empire, and grew accordingly. Many monuments in the city today date to this era. Many local Greek families fled at that time to Epirus and founded the Koumoutzades village (modern Ammotopos, Arta). Even there they were persecuted by the Ottomans and some of them found refuge in Tropaia of Gortynia. The bond between the inhabitants of Komotini, Ammotopos and Tropaia exists to this day.

In the first two decades after its conquest, until 1383, the city was the seat of a frontier march (uç) under Evrenos, confronting the Serbian territories of Macedonia. The walled city continued to be inhabited by locals, Gazi Evrenos also brought in Turkish settlers to the countryside around the town to stop any riots. During the prevailingly Ottoman rule of the area, it appears that the region was largely supported, and subsequent Ottoman censuses show that Muslim Turks quickly became the dominant element in the rural districts around the city. Evrenos also invested in the city as building camiiye (small mosque), an imaret, bath, and shops outside the city walls, establishing a waqf that according to Machiel Kiel became the "nucleus of Islamic life in Western Thrace". The 16th-century geographer Mehmed-i Ashik also mentions a hostel (imaret) built by Evrenos.