Parthenius or Parthenios (Greek: Παρθένιος) may refer to:

• Parthenius of Nicaea (1st-century BC–14 AD), Greek grammarian and poet
• Saint Parthenius (died 4th-century, Rome), Armenian saint and martyr from Rome, who suffered martyrdom during the reign of Decius
• Hierarch Parthenius of Lampsacus, bishop of Lampsacus in the 4th century, Greek Orthodox patron saint of cancer patients
• One of several Greek Patriarchs of Alexandria
• One of several Ecumenical Patriarchs of Constantinople
• The chief chamberlain of Domitian (died 96)

• A river which is now named Bartın River in northern Anatolia
• Bartın, a city in Turkey
• Mount Parthenion, Greece