Leontius or Leontios (died 705) was a Byzantine emperor.

Leontius or Leontios may also refer to:

• Leontius of Antioch or Leontius the Eunuch (4th century), Patriarch of Antioch 344–358
• Leontius (usurper) (died 488), Byzantine usurper
• Leontius of Byzantium (485–543), Byzantine theological writer
• Leontius II (archbishop of Bordeaux) (r. 542–564)
• Leontius (archbishop of Lyon) (early 6th century)
• Leontius of Jerusalem (6th century), Byzantine theological writer historically confused with Leontius of Byzantium
• Leontios of Neapolis (7th century), Byzantine theological writer
• Łewond (fl. late 8th century), Armenian priest and historian
• Leontius of Damascus (fl. late 8th century), Syrian monk and writer
• Leontius of Alexandria (11th century), Greek Patriarch of Alexandria 1052–1059
• Leontius of Constantinople (died after 1190), Ecumenical Patriarch of Constantinople 1189
• Leontius Pilatus (died 1366), Greek Calabrian scholar
• Saint Leontius of Monemvasia (1377–1452) Greek Orthodox ascetic
• Leontius (Turkevich) (1876–1965), Metropolitan of the North American Diocese of the Russian Orthodox Church 1950–1965