Dioclea or Dioklea, Dioclia or Dioklia, Diocleia or Diokleia (Ancient Greek: Διοκλεία, romanized: Diokleía), was a town of ancient Phrygia, inhabited during Roman and Byzantine times.^[1][2]

In Hellenic times it had a mint,^[3][4] under its king Elagabalus.^[5]

It was the see of a Christian bishop.^[6] Lequien, names only two known bishops of the town.^[7] Constantius (fl 431^[8] - 451^[9]) and Evander^[10] Another bishop, Gregorios, is attested in the first half of the 11th century. Diokleia was included in diocese lists until the 12th century.^[11]: 234 No longer the seat of a residential bishop, it remains a titular see of the Roman Catholic Church^[12] as well as the Eastern Orthodox Church (for which it is now a metropolitan titular see, with Kallistos Ware as its metropolitan until his death in August 2022).

Its site is located near Yeşilhisar in Asiatic Turkey.^[1][13] This site is located on the southwest flank of the Ahır Dağ, 84 km south of Kütahya. The only remains of the ancient settlement are a few old inscriptions and a capital dated to the early Byzantine period. The old name "Diokleia" is preserved in the nearby place called Dolay, or Doğla, a short distance to the south.^{[11]: 233–4}