SM UB-104 was a German Type UB III submarine or U-boat in the German Imperial Navy (German: Kaiserliche Marine) during World War I. She was commissioned into the German Imperial Navy on 15 March 1918 as SM UB-104.
UB-104 was sunk by mine in at the Northern Barrage on 19 September 1918.
See main article: Type UB III submarine. She was built by Blohm & Voss of Hamburg and following just under a year of construction, launched at Hamburg on 1 September 1917. UB-104 was commissioned later the same year under the command of Oblt.z.S. Ernst Berlin. Like all Type UB III submarines, UB-104 carried 10 torpedoes and was armed with a 8.82NaN2 deck gun. UB-104 would carry a crew of up to 3 officer and 31 men and had a cruising range of 7420nmi. UB-104 had a displacement of 519lk=inNaNlk=in while surfaced and 649t when submerged. Her engines enabled her to travel at 13.3kn when surfaced and when submerged.
| Date | Name | Nationality | Tonnage[1] | Fate[2] | |
|---|---|---|---|---|---|
| 2 August 1918 | Flevo X |  Netherlands | 111 | Sunk | |
| 2 August 1918 | Remke | Netherlands | 193 | Sunk | |
| 3 August 1918 | Cambrai |  France | 963 | Sunk | |
| 13 August 1918 | Frida |  Denmark | 395 | Sunk | |
| 13 August 1918 | Jönköping 1 |  Sweden | 1,546 | Sunk | |
| 14 August 1918 | Wallsend |  United Kingdom | 2,697 | Sunk | |
| 14 September 1918 | Gibel Hamam | United Kingdom | 647 | Sunk | |
| 15 September 1918 | Kendal Castle | United Kingdom | 3,885 | Sunk | |
| 16 September 1918 | Ethel | United Kingdom | 2,336 | Sunk | |
| 16 September 1918 | Lord Stewart | United Kingdom | 1,445 | Sunk | |
| 17 September 1918 | Ursa | Sweden | 1,740 | Sunk |