He did not. He renamed it as New Rome. The name Constantinopolis came after him. It was often just referred as polis. The name Istanbul is derived from "eis ta

He did not. He renamed it as New Rome. The name Constantinopolis came after him. It was often just referred as polis. The name Istanbul is derived from "eis tan polis" (to the city) used as a common phrase during Byzantian times. Turks kept using this old names as Konstantiniyye (Constantin's city in Arabic) Istanbul, both only referring to the walled part of the city till mid-20th century.