Demetrius I or Demetrios I may refer to:

  • Demetrius I of Macedon (337–283 BC), king of Macedon
  • Demetrius I of Bactria, Greco-Bactrian king (reigned c. 200–180 BC)
  • Demetrius I Soter (born 185 BC, reign 161–150 BC), ruler of the Hellenistic Seleucid Empire
  • Pope Demetrius I of Alexandria, ruled in 189–232
  • Demetrius Zvonimir of Croatia (died 1089), King of Croatia
  • Demetrius I of Georgia (c. 1093–1156), Georgian king
  • Demetrios I Kantakouzenos, Despot of the Morea in 1383
  • Demetrius I Starshy (died 1399), Duke of Bryansk
  • Demetrius I Qadi (1861–1925), Patriarch of the Melkite Greek Catholic Church
  • Demetrios I of Constantinople (1914–1991), Ecumenical Patriarch of Constantinople in 1972–1991

See also

  • Patriarch Dimitrije, Serbian Patriarch in 1920–1930