The Diocese of Macedonia (Latin: Dioecesis Macedoniae, Greek: Διοίκησις Μακεδονίας) was a diocese of the later Roman Empire, forming part of the praetorian prefecture of Illyricum. Its administrative centre was Thessaloniki.
The diocese was formed, probably under Constantine I (r. 306–337), from the division of the Diocletianian Diocese of Moesia. It included the provinces of Macedonia Prima, Macedonia Secunda or Salutaris (periodically abolished), Thessalia, Epirus vetus, Epirus nova, Achaea, and Crete. The Diocese of Macedonia, together with the Diocese of Dacia and (up to 379) the Diocese of Pannonia, made up the Prefecture of Illyricum.