君士坦丁堡（希腊语：Κωνσταντινούπολις、Κωνσταντινούπολη；拉丁语：Constantinopolis；奥斯曼土耳其语：قسطنطینیه；现代土耳其语：İstanbul）又译康斯坦庭堡，是土耳其最大城市伊斯坦堡的旧名，现在则指伊斯坦堡金角湾与马尔马拉海之间的地区。它曾经是罗马帝国、东罗马帝国、拉丁帝国和奥斯曼帝国的首都。

公元330年，罗马皇帝君士坦丁一世在拜占庭创建新都，命名为新罗马（拉丁语：Nova Roma；希腊语：Νέα Ρώμη），但该城普遍被以创建者之名称作君士坦丁堡。在公元12世纪时，君士坦丁堡是全欧洲规模最大且最为繁华的城市。

Constantinople (Greek:Κωνσταντινούπολις Konstantinoúpolis or Κωνσταντινούπολη Konstantinoúpoli; Latin:Constantinopolis; Ottoman Turkish:قسطنطینية, Qustantiniyye‎; Bulgarian:Цариград; Bosnian:Carigrad; Serbian Cyrillic:Цариград) was the capital city of the Roman/Byzantine Empire (330–1204 and 1261–1453), and also of the brief Latin (1204–1261), and the later Ottoman (1453–1924) empires. It was reinaugurated in 324 AD at ancient Byzantium, as the new capital of the Roman Empire by Emperor Constantine the Great, after whom it was named, and dedicated on 11 May 330.