ancient maritime town in Bithynia (today in Turkey)
For the Ecumenical Council of 451, see Council of Chalcedon.

Chalcedon (Χαλκηδών, sometimes transliterated as Chalkedon) was an ancient maritime town of Bithynia, in Asia Minor, almost directly opposite Byzantium, south of Scutari (modern Üsküdar). Today, in modern Turkish, Chalcedon is called Kadıköy and a district of Istanbul, Turkey.

Bithynia as a province of the Roman Empire, 125 AD

40°59′N 29°02′E / 40.983°N 29.033°E / 40.983; 29.033