Alaşehir (Turkish pronunciation: [aˈɫaʃehiɾ]), in Antiquity and the Middle Ages known as Philadelphia (Greek: Φιλαδέλφεια, i.e., "the city of him who loves his brother"), is a town and district of Manisa Province in the Aegean region of Turkey. It is situated in the valley of the Kuzuçay (Cogamus in antiquity), at the foot of the Bozdağ Mountain (Mount Tmolus in antiquity). The town is connected to İzmir by a 105 km (65 mi) railway.

It 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. It has about 45 mosques. There are small industries and a fair trade. From one of the mineral springs comes a heavily charged water popular around Turkey.

Within Turkey, the city's name is synonymous with the dried Sultana raisins, although cultivation for the fresh fruit market, less labour-intensive than the dried fruit, has gained prominence in recent decades. As Philadelphia, Alaşehir was a highly important center in the Early Christian and Byzantine periods. It remained a strong center of Orthodox Christianity until the early 20th century, and remains a titular see of the Roman Catholic Church.