Joannicius, also Ioannikios (Greek: Ιωαννίκιος), Joanikije (Serbian: Јоаникије), Ioannikiy (Russian: Иоанникий), Anikiy (Russian: Аникий), Ioannykiy (Ukrainian: Іоанникій), Onykiy (Ukrainian: Оникій), may refer to:
- Joannicius the Great, 8th-century Byzantine Christian saint
- Joannicius of Ochrid, Archbishop of Ohrid (13th century)
- Joanikije I, Archbishop of the Serbian Orthodox Church 1272–1276
- Joanikije II, first Serbian Patriarch, Wonderworker, reigned 1346-1354
- Joanikije II, Metropolitan of Montenegro, since 2021
- Joannicius of Devič, died 1430
- Patriarch Joannicius I of Constantinople, reigned 1524–1525
- Patriarch Joannicius II of Constantinople, reigned four times in 1646–1656
- Patriarch Joannicius III of Constantinople, reigned 1761–1763; Patriarch of the Serbs 1739–1746
- Patriarch Joannicius of Alexandria, Greek Patriarch of Alexandria 1645–1657
- Joannicius, Metropolitan of Moscow, reigned 1882-1891
- Joanikije Lipovac, Metropolitan of Montenegro, died 1945