| Megalonisi | |
| Native Name: | Μεγαλονήσι |
| Native Name Lang: | el |
| Nickname: | --> |
| Coordinates: | 39.2164°N 25.8366°W |
| Archipelago: | Aegean Sea |
| Area M2: | or |
| Area Ha: | --> |
| Length M: | --> |
| Width M: | --> |
| Coastline M: | --> |
| Country: | Greece |
| Country Area M2: | or |
| Country Area Ha: | --> |
| Country1 Area M2: | or |
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Megalonisi (Greek, Modern (1453-);: Μεγαλονήσι), also Nisiopi (Greek, Modern (1453-);: Νησιώπη), is a long island near the west coast of the island Lesbos, North Aegean, Greece.[1] It is situated in front of Sigri's harbour, and stretches across the mouth of the bay and acts as a buffer to the prevailing winds. In the middle stands Megalonisi Lighthouse to help ships navigate in the rough east Aegean Sea.[2]