SM UB-73 was a German Type UB III submarine or U-boat in the German Imperial Navy (de|Kaiserliche Marine) during World War I. She was commissioned into the German Imperial Navy on 2 October 1917 as SM UB-73.
UB-73 was serving in the Mediterranean. On 21 November 1918 she was surrendered to France as required by the regulations of the Armistice with Germany.
See main article: Type UB III submarine. UB-72 was ordered by the GIN on 23 September 1916.
She was built by AG Vulcan of Hamburg and following just under a year of construction, launched at Hamburg on 11 August 1917. UB-73 was commissioned later that same year . Like all Type UB III submarines, UB-73 carried 10 torpedoes and was armed with a 8.82NaN2 deck gun. UB-73 would carry a crew of up to 3 officer and 31 men and had a cruising range of 8420nmi. UB-73 had a displacement of 508lk=inNaNlk=in while surfaced and 639t when submerged. Her engines enabled her to travel at 13.4kn when surfaced and when submerged.
| Date | Name | Nationality | Tonnage[1] | Fate[2] | |
|---|---|---|---|---|---|
| 7 April 1918 | Catriena |  Netherlands | 115 | Sunk | |
| 11 April 1918 | Myrtle Branch |  United Kingdom | 3,741 | Sunk | |
| 14 April 1918 | Chelford | United Kingdom | 2,995 | Sunk | |
| 16 April 1918 | Ladoga | United Kingdom | 1,917 | Sunk | |
| 16 April 1918 | Lodaner | United Kingdom | 3,291 | Sunk | |
| 18 April 1918 | Dalegarth Force | United Kingdom | 684 | Sunk | |
| 23 June 1918 | Mountain Laurel |  Norway | 705 | Sunk | |
| 24 June 1918 | 495 | Sunk | |||
| 25 June 1918 | Orissa | United Kingdom | 5,358 | Sunk |