Eleutherius, Eleutherus or Eleuterus may refer to:
- Saints
- 2nd century Pope Eleuterus (feast day: May 26)
- Eleutherius of Rocca d'Arce (feast day: May 29)
- Eleutherius of Nicomedia (feast day: October 2)
- Eleutherius of Tournai, bishop of Tournai, 5th century evangelist of the Franks
- the martyr Eleutherius of Constantinople
- Eleutherius and Antia (feast day: April 18), martyrs
- the martyred companion of Saint Denis (martyred c.250, feast day: October 9)
- Orthodox church patriarchs and exarchs
- Eleutherius of Byzantium, Patriarch of Constantinople (129–136)
- Eleutherius, Greek Patriarch of Antioch (1023–1028)
- Eleutherius, Greek Patriarch of Alexandria (1175–1180)
- Eleutherius, 7th century Exarch of Ravenna