Basilinopolis was a small village in Bithynia Prima, which obtained the rank of a city under, or perhaps shortly before, Julian the Apostate, whose mother was Basilina.
Its exact site is not known. W. M. Ramsay, placed it on the western side of the Lake of Nicaea, near Pazarköy, between Kios (now Gemlik) and Nicaea (Iznik)., as did the 2013 Annuario Pontificio.
The first known bishop, Alexander, was consecrated by John Chrysostom about 400. Other bishops are:
At the Council of Chalcedon (451) the metropolitans of Nicomedia and Nicaea were in sharp dispute about jurisdiction over the see of Basilinopolis. The council decided to assign it as a suffragan of Nicomedia. It was still reckoned as such in 1170 under Manuel Comnenus. The see does not figure in a Notitia episcopatuum of the Ecumenical Patriarchate of Constantinople after the 15th century, probably indicating that the city was destroyed in the Osmanli conquest.
Basilinopolis is listed by the Catholic Church as a titular see.
This article incorporates text from a publication now in the public domain: Herbermann, Charles, ed. (1913). "". Catholic Encyclopedia. New York: Robert Appleton.