| Official Name: | Fornais |
| Other Name: | Furnace Island |
| Settlement Type: | Island |
| Pushpin Map: | Ireland |
| Pushpin Label Position: | right |
| Pushpin Map Caption: | Location in Ireland |
| Coordinates: | 53.2551°N -9.7424°W |
| Subdivision Type: | Country |
| Subdivision Name: | Ireland |
| Subdivision Type1: | Province |
| Subdivision Type3: | County |
| Subdivision Name1: | Connacht |
| Subdivision Name3: | County Galway |
| Leader Title1: | Dáil Éireann |
| Leader Name1: | Galway West |
| Unit Pref: | Metric |
| Population: | 66 |
| Population As Of: | 2022 |
| Population Footnotes: | [1] |
| Population Density Km2: | auto |
| Timezone1: | WET |
| Utc Offset1: | +0 |
| Timezone1 Dst: | IST (WEST) |
| Utc Offset1 Dst: | -1 |
| Footnotes: | As this is a Gaeltacht, Fornais is the only official name. |
| Blank Name: | Irish Grid Reference |
Furnace Island, or simply Furnace (officially known by its Irish name Fornais),[2] is one of the inhabited South Connemara Islands of County Galway, in Ireland. It is connected to the mainland by a bridge to the island Lettermullan.