| Losorion | |
| Map Type: | Georgia |
| Coordinates: | 41.6633°N 41.6825°W |
| Location: | Lazica (Batumi, Adjara, Georgia |
| Region: | South Caucasus |
| Type: | Fortification |
| Epochs: | Late Antiquity |
| Event: | Lazic War |
Losorion or Lysiris (Greek, Ancient (to 1453);: Λοσόριον), was a Byzantine (Roman) fortification on the eastern Black Sea coast, in Lazica in what is now Batumi, western Georgia. In the 6th century, it was constructed by Byzantine emperor Justinian I,[1] and due to its strategic location became a battleground of the 541–562 Lazic War between Rome and Sasanian Persia (Iran). It was identified with the Medieval fortress of Batumi, known as Tamaris Tsikhe, i.e. Queen Tamar's Castle.[2]