Edirne (historic Adrianople, Greek Αδριανούπολις, Bulgarian Одрин) is a city in Eastern Thrace near the Hebros (Maritsa) River. It was on the major military road running from Belgrade to Sofia and Constantinople.

Hadrian refounded the Thracian settlement of Uskudama around 125 and renamed it Hadrianopolis. It was an important stronghold protecting Constantinople from invasions from the north, but is rarely mentioned as an administrative center. Adrianople is known to be a bishopric by the end of the 4th century, but its place in the ecclesiastical hierarchy later declined.

Adrianople was located on the intersection of important strategic routes, making it a frequent center of military activity: Constantine I defeated Licinius near Adrianople in 324; Valens was routed here by the Goths in 378; and the Avars besieged Adrianople but failed to capture it in 586. Adrianople was a strong point in wars against the Bulgarians in the 9th and 10th centuries, though both Krum and Symeon managed to seize Adrianople temporarily.

Adrianople was a center of the Macedonian nobility, especially in the 11th and 12th centuries. It produced at least three usurpers: Leo Tornikios, Nikephoros Bryennios, and Alexios Branas. Conversely, Macedonian troops supported Constantinople against eastern generals during the revolts of Nikephoros Phokas and Isaac Komnenos. In the 11th century resistance to the Pechenegs was based at Adrianople. Frederick I Barbarossa occupied the city and in 1190 signed there a treaty with Constantinople. Kalojan defeated Baldwin I of Constantinople at Adrianople in 1205. In the 13th century the city changed hands several times, being captured by the armies of Nicaea, Epiros, and Bulgaria. John III Vatatzes established Nicaean rule over Adrianople in 1242-46. In 1307 the Catalan Grand Company besieged it. The Ottoman seized it perhaps around 1369, after which it served as the Ottoman capital until the conquest of Constantinople in 1453.

Hagia Sophia, an important domed quatrefoil church from the 5th or 6th century, was photographed in the 19th century. Some sections of its walls, including the so-called Macedonian Tower, have survived. It is home to many important Ottoman mosques building in the 14th-16th centuries.