SM UB-129 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 11 June 1918 as SM UB-129.
UB-129 was lost 31 October 1918 in Fiume (45.3167°N 40°W) after the surrender of Austria-Hungary.
See main article: Type UB III submarine. She was built by AG Weser of Bremen and following just under a year of construction, launched at Bremen on 11 May 1918. UB-129 was commissioned later the same year under the command of Kptlt. Karl Neumann. Like all Type UB III submarines, UB-129 carried 10 torpedoes and was armed with a 10.52NaN2 deck gun. UB-129 would carry a crew of up to 3 officer and 31 men and had a cruising range of 7280nmi. UB-129 had a displacement of 512lk=inNaNlk=in while surfaced and 643t when submerged. Her engines enabled her to travel at 13.9kn when surfaced and when submerged.
| Date | Name | Nationality | Tonnage[1] | Fate[2] | |
|---|---|---|---|---|---|
| 16 September 1918 | Buenaventura |  United States | 4,881 | Sunk | |
| 22 September 1918 | Erik |  Denmark | 217 | Sunk |