| Sydney Island | |
| Map: | Australia Queensland |
| Location: | Gulf of Carpentaria |
| Archipelago: | Wellesley Islands |
| Major Islands: | Mornington Island |
| Length Km: | 5 |
| Country: | Australia |
| Country Admin Divisions Title: | State |
| Country Admin Divisions: | Queensland |
Sydney Island is situated in the Gulf of Carpentaria and is one if the islands of the Wellesley Islands group. It is about long and just to the south of the major island in the group Mornington Island.