Founded in antiquity as Philadelphia (Greek: Φιλαδέλφεια, i.e., "the city of him who loves his brother"), the town was known as such until it was conquered by the Ottomans in 1390.

Alaşehir stands on elevated ground commanding the extensive and fertile plain of the Gediz River (Hermus in antiquity), presenting an imposing appearance when seen from a distance.

[6] The Turkish name Alaşehir, which translates as "multicolored town", is first attested in the memoir of the 13th-century historian Ibn Bibi.

[7] The town was founded by King Attalus II Philadelphus (r. 159–138 BC) of Pergamon with the Greek name "Philadelphia".

[7][8] According to numismatic evidence, Philadelphia was briefly given the Latin name "Neocaesarea" during the reigns of the Roman emperors Caligula (r. 37–41) and Claudius (r. 41–54).

[13] Lacking an heir, Attalus III Philometer, the last of the Attalid kings of Pergamum, bequeathed his kingdom, including Philadelphia, to his Roman allies when he died in 133 BC.

In AD 17, the city suffered badly in an earthquake, and Roman Emperor Tiberius relieved it of having to pay taxes (Tacitus Annales 2.47, cf.

Evidence from coinage reveals that Caligula helped the city; under Vespasian, Philadelphia received his cognomen, Flavia.

A small theatre, located at the northern edge of Toptepe Hill, is all that remains of Roman Philadelphia.

Although several ancient cities bore the name of Philadelphia,[15] it is generally agreed to be the one listed among the seven churches written to by John in the Book of Revelation.

The city's history of earthquakes may lie behind the reference to making her church "a pillar in the temple" (Revelation 3:12).

[17] Philadelphia was a prosperous Byzantine city that was called the "little Athens" in the 6th century AD because of its festivals and temples.

In the 11th to the 15th centuries AD, it was the seat of the doux (governor) and stratopedarches (military commander) of the Thrakesion theme.

[19] In the 14th century, Philadelphia was made the metropolis of Lydia by the Greek Orthodox patriarch of Constantinople, a status that it still holds.

[20] By the 14th century, the city was surrounded by Ottoman emirates but maintained nominal allegiance to the Byzantine emperor.