Diocletianopolis or Diokletianoupolis (Διοκλητιανούπολις) may refer to a number of places in the ancient world named after Emperor Diocletian.
- Diocletianopolis (Palestine), in modern Israel
- Diocletianopolis (Thebais), in modern Egypt
- Diocletianopolis (Thrace), in modern Bulgaria
- Diocletianopolis (Kastoria) in Greece
- Diocletianopolis (Pella) in Greece