| Name: | W 4 |
| Type: | Submarine |
| Keel: | 20/03/1914 |
| Launched: | 11/09/1915 |
| Completed: | 27/06/1916 |
| Builder: | Armstrong, Whitworth & Co Ltd |
| Yard: | Elswick |
| Yard Number: | 871 |
| Dimensions: | 490disp subm, 321disp surf, 149.9 x 17.9ft |
| Engines: | 2 x oil engines, 8cyl, 2 x electric motors, 740hp |
| Engines by: | Lambert-Schneider |
| Propulsion: | 2 x Screws, 8.0knots subm, 13.0knots surf |
| Construction: | Steel |
| Armament: | 1 x 3ins gun, 6 x 18ins torpedoes |
| History: | |
| 06/1916 | British Royal Navy |
| 23/08/1916 | Transferred to the Italian Navy |
| 04/08/1917 | Sank |
| Comments: | The Class was known as the Armstrong-Laubeuf type, having |
| been built in the UK for the Italian Navy | |
| 04/08/1917: Mined and sunk 150miles west of Bari. 23 crew lost |
