Tre Fratelli D.
| Name | Tre Fratelli D. |
| Type | Sailing vessel |
| GRT | 190 tons |
| Country |  Italian |
| Built | 1913 |
| Builder | A. Codecasa, Viareggio |
| Operator | T. Domenici, Viareggio |
| History | Wooden brigantine |
U-boat attacks on Sailing vessel Tre Fratelli D.
| Date | U-boat | Loss type | Position | Location | Route | Cargo | Casualties | |
| 1 | 28 Oct 1916 | U 21 (Otto Hersing) | Sunk | SE coast of Corsica | 41° 26'N, 9° 42'E |
Position of attack on Tre Fratelli D.
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