title: Dionysius I
text: # Dionysius I
  
  Dionysius I may refer to:
  
  * Dionysius I of Syracuse (ca. 432–367 BC), Greek tyrant of Syracuse
  * Dionysius I (Syriac Patriarch), or Dionysius Telmaharensis (died 845), Patriarch of the Syriac Orthodox Church
  * Dionysius I, Metropolitan of Moscow (died 1385)
  * Patriarch Dionysius I of Constantinople (died 1492), Patriarch of Constantinople
  * Mar Dionysius I (died 1808), Metropolitan of the Malankara Church
  