Nakoleia (Greek: Νακώλεια), latinized as Nacolia or Nacolea, was an ancient and medieval city in Phrygia. It corresponds to present-day Seyitgazi, Eskişehir Province in the Central Anatolia region of Turkey.
It was a town of Phrygia Salutaris, taking its name in legend from the nymph Nacola, and had no history in antiquity. It was there that Valens defeated the usurper Procopius in 366; under Arcadius it was occupied by a garrison of Goths under Tribigild who revolted against the emperor in 399. In 768, it was seized by the Arabs.
At first dependent on Synnada, the see became autocephalous between 787 and 862, and metropolitan between 1035 and 1066. Seven of its bishops are known, among them being Constantine, one of the chief supporters of Iconoclasm under Leo the Isaurian, who pretended to abjure his error before the patriarch, St. Germanus, and was condemned as an heresiarch at the Second Council of Nicaea (787). Nakoleia remains a titular see in the Catholic Church.