List of shipwrecks in September 1918

The list of shipwrecks in September 1918 includes ships sunk, foundered, grounded, or otherwise lost during September 1918.

1 September

 * Ami de Dieu (🇫🇷 France): World War I: The trawler was sunk in the Atlantic Ocean (approximately 47.53333°N, -8.91667°W) by SMU U-53.
 * SS City of Glasgow (1906) ( undefined): World War I: The passenger ship was torpedoed and sunk in the Atlantic Ocean 21 nmi east of the Tuskar Rock, Ireland (52.28333°N, -5.63333°W) by SMU UB-118 with the loss of twelve lives.
 * Etoile Polaire (🇫🇷 France): World War I: The trawler was shelled and sunk in the Atlantic Ocean 176 nmi off Penmarc'h, Finistère (47.53333°N, -8.91667°W) by SMU U-53 with the loss of a crew member.
 * Libertador (🇵🇹 Portugal): World War I: The trawler was scuttled west of Gibraltar by SMU U-22 (Germany).
 * SS Mesaba (1898) ( undefined): World War I: The cargo ship was torpedoed and sunk in the Atlantic Ocean 21 nmi east of the Tuskar Rock (52.28333°N, -5.63333°W) by SMU UB-118 with the loss of twenty of her crew.

2 September

 * Hirondelle (🇫🇷 France): World War I: The fishing vessel was sunk in the Atlantic Ocean (47.53333°N, -8.91667°W) by SMU U-53.
 * Nicolazic (🇫🇷 France): World War I: The fishing vessel was sunk in the Atlantic Ocean (47.53333°N, -8.91667°W) by SMU U-53 . Her crew survived.
 * SS San Andres (1918) ( undefined): World War I: The cargo ship was torpedoed and sunk in the Mediterranean Sea 40 nmi north by west of Port Said, Egypt by SMU U-65 (Germany) . Her crew survived.
 * SS Stortind (🇳🇴 Norway): World War I: The cargo ship was scuttled in the Atlantic Ocean 360 nmi north of the Azores, Portugal by SMU U-155 . Her crew survived.

3 September

 * SS Brava (1893) (🇵🇹 Portugal): World War I: The cargo ship was torpedoed and sunk in the Atlantic Ocean 3.5 nmi north west of Trevose Head, Cornwall, United Kingdom (50.56667°N, -5.1°W) by SMU UB-125 with the loss of seventeen of her crew.
 * SS Bogstad (1910) (🇳🇴 Norway): The cargo ship departed from Brest, Finistère, France for Cardiff, Glamorgan, United Kingdom. No further trace, presumed foundered with the loss of all hands.
 * SS Highcliffe (2842) ( undefined: World War I: The cargo ship was torpedoed and sunk in the Atlantic Ocean 13 nmi south east of the Tuskar Rock, Ireland (51.93333°N, -5.9°W) by SMU UB-87 with the loss of a crew member.
 * SS Lake Owens (1918) (🇺🇸 United States): World War I: The cargo ship was sunk in the Atlantic Ocean 3.5 nmi north west by west of Trevose Head (50.53333°N, -5.13333°W) by SMU UB-125 with the loss of five of her crew.

4 September

 * SS Arum (1914) ( undefined): World War I: The cargo ship was torpedoed and sunk in the Mediterranean Sea 40 nmi east of Pantelleria, Italy (36.83333°N, 12.83333°W) by SMU UC-54 . Her crew survived.
 * SS Bogstad (1910) (🇳🇴 Norway): World War I: The cargo ship was sunk in the Bristol Channel 18 nmi south of Lundy Island, Devon, United Kingdom by SMU UB-125 with the loss of all twelve of her crew.
 * SS Dora (1913) (🇺🇸 United States): World War I: The cargo ship was sunk in the Atlantic Ocean off the coast of France (49.43333°N, -12.6°W) by SMU U-82 . Her crew survived.
 * Richard (🇳🇴 Norway): World War I: The sailing vessel was sunk in the Mediterranean Sea off Majorca, Spain (39.81667°N, 1.85°W) by SMU U-34 (Germany) . Her crew survived.
 * Santa Maria (🇵🇹 Portugal): World War I: The trawler was scuttled in the Atlantic Ocean off Peniche by SMU U-22 (Germany).
 * ST Villa Franca (🇵🇹 Portugal): World War I: The tug was shelled and sunk in the Atlantic Ocean off Lisbon by SMU U-22 (Germany).
 * SS War Firth ( undefined): World War I: The cargo ship was torpedoed and sunk in the Atlantic Ocean 33 nmi south by west of The Lizard, Cornwall by SMU U-53 with the loss of eleven crew.

5 September

 * USS Mount Vernon (ID-4508) : World War I: The troopship was torpedoed and damaged in the Atlantic Ocean 200 nmi off the coast of France by SMU U-82 with the loss of 36 of her crew. She was subsequently repaired and returned to service.
 *  Rio Mondego (🇵🇹 Portugal): World War I: The schooner was damaged by scuttling charges in the Atlantic Ocean 40 nmi off Land's End, Cornwall, United Kingdom. The charges were placed by SMU U-53 . She was towed to the Isles of Scilly and beached. Despite being placed under guard, some of her cargo of port was liberated by the locals.
 * SMU UC-91 : The Type UC III submarine collided with SS Alexandra Woermann ( German Empire) in the Baltic Sea (54.35°N, 10.16667°W) with the loss of 17 crew. She was raised on 6 September, repaired and returned to service.

6 September

 * SS Audax (1903) ( undefined): World War I: The coaster was torpedoed and sunk in the North Sea 6.5 nmi east by north of Robin Hood's Bay, Yorkshire (54.48333°N, -0.35°W) by SMU UB-80 with the loss of three of her crew.
 * SS Milly (1904) ( undefined): World War I: The collier was torpedoed and sunk in the Atlantic Ocean 2.25 nmi west by south of Tintagel Head, Cornwall (50.5°N, -4.86667°W) by SMU UB-87 with the loss of two of her crew.

7 September

 * SS Bellbank (1901) ( undefined): World War I: The cargo ship was torpedoed and sunk in the Mediterranean Sea 25 nmi south south west of the Île du Planier, Bouches-du-Rhône, France (42.8°N, 5.13333°W) by SMU UC-67 with the loss of a crew member.
 * SS Ruysdael (1912) ( undefined): World War I: The cargo ship was torpedoed and sunk in the Atlantic Ocean 228 nmi west by south of Ouessant, Finistère, France (46.88333°N, -10.11667°W) by SMU U-105 with the loss of twelve crew.
 *  Santa Maria (🇵🇹 Portugal): The barque was destroyed by fire in the Atlantic Ocean (-13.41667°N, -15°W). Her crew survived.
 *  Sophia (🇵🇹 Portugal): World War I: The schooner was sunk in the Atlantic Ocean off the coast of Newfoundland by SMU U-155.
 * SS Vicenza (1909) ( undefined): World War I: The cargo ship was sunk in the Mediterranean Sea south of Salonica, Greece (39.7°N, 23.3°W) by SMU UB-42.

8 September

 * HMS Nessus (1915) : The Admiralty M-class destroyer collided with HMS Amphitrite (1898) in the North Sea and sank.

9 September

 * SS Dorisbrook (1915) ( undefined): The collier collided with HMS Orbita and sank in the Pacific Ocean off the coast of Peru. Her crew were rescued by HMS Orbita.
 * Helvetia (🇳🇴 Norway): World War I: The sailing vessel was sunk in the North Sea 22 nmi west south west of Lindesnes, Vest-Agder by SMU U-80 . Her crew survived.
 * SS Missanabie (1914) ( undefined): World War I: The ocean liner was torpedoed and sunk in the Irish Sea 51.18333°N, -7.41667°W) by SMU UB-87 with the loss of 45 lives.
 * SS Taurus (1902) (🇳🇴 Norway): World War I: The cargo ship was sunk in the North Sea 1 nmi north of Scarborough, Yorkshire, United Kingdom by SMU UB-80 with the loss of six of her crew.
 * SMU U-92 : World War I: The Type U 87 submarine struck a mine in the North Sea (59°N, -1.5°W) and sank with the loss of all 39 crew.
 * SS War Arabis ( undefined): World War I: The cargo ship was torpedoed and sunk in the Mediterranean Sea 88 nmi north by east of Cape Sigli, Algeria (38.13333°N, 5.5°W) by SMU U-34 (Germany) . Her crew survived.

10 September

 * SMU UB-83 : World War I: The Type UB III submarine was depth charged and sunk in the North Sea off the Orkney Islands, United Kingdom (58.46667°N, -1.83333°W) by HMS Ophelia (1915) with the loss of all 37 crew.

12 September
For the scuttling of the Danish schooner Skjold on this date, see the entry for 3 August 1918.
 * SS Galway Castle (1911) ( undefined): World War I: The ocean liner was torpedoed and damaged in the Atlantic Ocean 160 nmi south west of the Fastnet Rock (48.83333°N, -10.66667°W) by SMU U-82 . She was taken in tow but sank on 15 September with the loss of 143 lives.
 * SS Leixões (1890) (🇵🇹 Portugal): World War I: The cargo ship was torpedoed and sunk in the Atlantic Ocean 200 nmi off the coast of the United States by SMU U-155.
 * HMS Sarnia : World War I: The armed boarding steamer was sunk in the Mediterranean Sea off Alexandria, Egypt (31.96667°N, 30.91667°W) by SMU U-65 (Germany) with the loss of 55 crew.

13 September

 * SS Amiral Charner (1902) (🇫🇷 France): World War I: The cargo ship was sunk in the Mediterranean Sea 44 nmi west of Pantellaria, Italy (36.6°N, 12.96667°W) by SMU U-41 (Austria-Hungary).
 * SS Buffalo (1866) ( undefined): World War I: The coaster was torpedoed and sunk in the Irish Sea of Corsewall Point, Wigtownshire by SMU UB-64 with the loss of ten of her crew.
 * SS M. J. Craig (1898) ( undefined): World War I: The coaster was torpedoed and sunk in the Irish Sea 7 nmi north east of Black Head, County Antrim by SMU UB-64 with the loss of four of her crew.
 * SS Setter (1906) ( undefined): World War I: The passenger ship was torpedoed and sunk in the Irish Sea 9 nmi north west of Stranraer, Wigtownshire by SMU UB-64 with the loss of nine of her crew.

14 September

 * Agios Nicolas (🇬🇷 Greece): World War I: The sailing vessel was sunk in the Mediterranean Sea 10 nmi south east of Paphos by SMU U-27 (Austria-Hungary) . Her crew survived.
 * SS Gibel Hamam (1895) ( undefined): World War I: The coaster was torpedoed and sunk in the English Channel 15 nmi south of Portland Bill by SMU UB-104 with the loss of 21 of her crew.
 * Ioanna No.45 ( undefined): World War I: The sailing vessel was sunk in the Mediterranean Sea by SMU U-65 (Germany).
 * SS Neotsfield (1906) ( undefined): World War I: The cargo ship was torpedoed and sunk in the Irish Sea 1.5 nmi off the Skulmartin Lightship ( undefined) (54.7°N, -5.38333°W) by SMU UB-64 . Her crew survived.
 * SMU UB-113 : World War I: The Type UB III submarine departed Zeebrugge, West Flanders, Belgium on patrol. No further trace, lost with all 39 crew.

15 September

 * Ioanna No.37 ( undefined): World War I: The sailing vessel was sunk in the Mediterranean Sea by SMU U-65 (Germany).
 * Energy ( undefined): World War I: The sailing vessel was shelled and sunk in the Irish Sea 14 nmi east south east of the Codling Bank Lightship ( undefined) by SMU UB-64.
 *  Joseph Fisher ( undefined): World War I: The two-masted schooner was shelled and sunk in the Irish Sea 16 nmi east north east of the Codling Bank Lightship ( undefined) by SMU UB-64.
 * SS Kendal Castle (1910) ( undefined): World War I: The cargo ship was torpedoed and sunk in the English Channel 4 nmi south east of Berry Head, Devon by SMU UB-104 with the loss of eighteen of her crew.
 *  Mary Fanny ( undefined): World War I: The ketch was shelled and sunk in the Irish Sea 14 nmi east south east of the Codling Bank Lightship ( undefined) by SMU UB-64.

16 September

 * SS Acadian (1908) ( undefined): World War I: The cargo ship was torpedoed and sunk in the Atlantic Ocean 11 nmi south west by west of Trevose Head, Cornwall (50.41944°N, -5.26611°W) by SMU UB-117 with the loss of 25 of her 26 crew.
 * USS Buena Ventura (ID-1335) : World War I: Convoy OV 31: The cargo ship was torpedoed and sunk in the Atlantic Ocean 200 nmi north west of Spain (44.6°N, -13.16667°W) by SMU UB-129 with the loss of eighteen of her crew. Survivors were rescued by Lola (🇪🇸 Spain) and FRENCH DESTROYER Temeraire.
 * SS Ethel (1898) ( undefined): World War I: The cargo ship was torpedoed and sunk in the English Channel 8 nmi south east of Berry Head, Devon by SMU UB-104 . Her crew survived.
 * HMS Glatton (1914) : The Gorgon-class monitor caught fire at Dover, Kent and was scuttled by HMS Cossack (1907) and HMS Myngs (1914) (both ) with the loss of 79 of her 305 crew.
 * SS G. Voyazides (1904) (🇬🇷 Greece): World War I: The cargo ship was torpedoed and sunk in the Gulf of Lion by SMU UC-67 with the loss of eighteen of her crew.
 * SS Lord Stewart (1905) ( undefined): World War I: The collier was torpedoed and sunk in the English Channel 6 nmi east of Hope's Nose, Devon (50.5°N, -3.28333°W) by SMU UB-104 with the loss of a crew member.
 * SS Madryn (1916) ( undefined): World War I: The collier was torpedoed and sunk in the Atlantic Ocean 5 nmi north north east of Trevose Head (50.63333°N, -5.01667°W) by SMU U-82 . Her crew survived.
 * SS Philomel (1917) ( undefined): World War I: The cargo ship was torpedoed and sunk in the Bay of Biscay 12 nmi south east by east of the Glénan Islands, Finistère (47.71667°N, -3.68333°W) by SMU UB-88 . Her crew survived.
 * SS Serula (1905) ( undefined): World War I: The cargo ship was torpedoed and sunk in the Irish Sea 13.5 nmi north east of Strumble Head, Pembrokeshire by SMU UB-64 with the loss of seventeen crew.
 * SS Star of Poland (🇺🇸 United States): The cargo ship was wrecked at Chiba, Japan.
 * SS Tasman (1912) ( undefined): World War I: The cargo liner was torpedoed and sunk in the Atlantic Ocean 220 nmi north by west of Cape Villano, Spain by SMU U-46 with the loss of fourteen crew.
 * SS Wellington (1905) ( undefined): World War I: The cargo ship was torpedoed and sunk in the Atlantic Ocean 175 nmi north west of Cape Villano (45.8°N, -10.96667°W) by SMU U-118 with the loss of five of her crew.

17 September

 * Cairo (🇪🇬 Egypt): World War I: The sailing vessel was shelled and sunk in the Mediterranean Sea by an enemy submarine.
 * SS Lavernock (1888) ( undefined): World War I: The cargo ship was torpedoed and sunk in the Atlantic Ocean 5 nmi south west of Trevose Head, Cornwall 50.46667°N, -5.1°W by SMU UB-117 . Her crew survived.
 * SS Muriel (1898) ( undefined): World War I: The collier was torpedoed and sunk in the North Sea 3.5 nmi north east of Peterhead, Aberdeenshire (57.535°N, -1.73778°W) by SMU UC-58 . Her crew survived.
 * Portaritissa ( undefined): World War I: The sailing vessel was sunk in the Mediterranean Sea (35.65°N, 26.13333°W) by SMU U-27 (Austria-Hungary) . Her crew survived.
 * Sofia ( undefined): World War I: The sailing vessel was sunk in the Mediterranean Sea (35.65°N, 26.13333°W) by SMU U-27 (Austria-Hungary) . Her crew survived.
 * SS Ursa (1902) (🇸🇪 Sweden): World War I: The cargo ship was torpedoed and sunk in Lyme Bay by SMU UB-104 . Her crew survived.

18 September

 * Adelphotis (🇬🇷 Greece): World War I: The sailing vessel was sunk in the Mediterranean Sea (36.23333°N, 25.41667°W) by SMU U-27 (Austria-Hungary) . Her crew survived.
 * Agios Amma (🇬🇷 Greece): World War I: The sailing vessel was sunk in the Mediterranean Sea (36.23333°N, 25.41667°W) by SMU U-27 (Austria-Hungary) . Her crew survived.
 * SS Buffalo (1903) (🇫🇷 France): World War I: The cargo ship was torpedoed and sunk in the Atlantic Ocean 2 nmi east of St Agnes Head, Cornwall, United Kingdom (50.31667°N, -5.3°W) by SMU UB-117.
 * SS Helena (🇺🇸 United States): The cargo ship ran aground on West Chicken Island, Lake Erie. She broke in two on 25 September and was a total loss.
 * SS John O. Scott (1906) ( undefined): World War I: The cargo ship was torpedoed and sunk in the Atlantic Ocean 9 nmi west by north of Trevose Head, Cornwall (50.53333°N, -5.26667°W) by SMU UB-117 with the loss of eighteen of her crew.
 * SS Ledaal (1901) (🇳🇴 Norway): World War I: The cargo ship was scuttled in the Atlantic Ocean (33.83333°N, -20.08333°W) by SMU U-157 with the loss of a crew member.
 * SS Primo (1908) ( undefined): World War I: The cargo ship was torpedoed and sunk in the Atlantic Ocean 3.5 nmi north north west of the Godrevy Lighthouse, Cornwall (50.28333°N, -5.46667°W) by SMU UB-117 . Her crew survived.

19 September

 * Agios Spiridon (🇬🇷 Greece): World War I: The sailing vessel was sunk in the Mediterranean Sea (36.06667°N, 24°W) by SMU U-27 (Austria-Hungary) . Her crew survived.
 * SS Barrister (1916) ( undefined): World War I: The cargo ship was torpedoed and sunk in the Irish Sea 9 nmi west of the Chicken Rock Lighthouse, Isle of Man by SMU UB-64 with the loss of 30 crew.
 * Belliqueux (🇫🇷 France): World War I: The vessel struck a mine and sank in the Bay of Biscay 1 nmi off the Tevenec Lighthouse, Île de Sein, Finistère.
 *  Erik (🇩🇰 Denmark): World War I: The three-masted schooner was shelled and damaged in the Atlantic Ocean 75 nmi west of Cape Roca, Spain (38.08333°N, -10.28333°W) by SMU UB-129 . She foundered three days later.
 * SS Fanny (1887) (🇸🇪 Sweden): World War I: The cargo ship was sunk in the Raz de Sein by SMU UB-88 . Her crew survived.
 * SS Gordon C. (Newfoundland): The cargo ship was destroyed by fire 12 nmi north east of Grate's Cove.

20 September

 * Aghios Nicolaos (🇬🇷 Greece): World War I: The sailing vessel was scuttled in the Mediterranean Sea (36.95°N, 22.08333°W) by SMU U-27 (Austria-Hungary) . Her crew survived.
 * Aghios Nicolas (🇬🇷 Greece): World War I: The sailing vessel was sunk in the Mediterranean Sea (36.43333°N, 22.33333°W) by SMU U-27 (Austria-Hungary) . Her crew survived.
 * Aghios Spiridon (🇬🇷 Greece): World War I: The sailing vessel was sunk in the Mediterranean Sea (36.43333°N, 22.33333°W) by SMU U-27 (Austria-Hungary) . Her crew survived.
 * Angelina Pasquale ( undefined): World War I: The sailing vessel was sunk in the Mediterranean Sea off Sicily by SMU UB-105.
 * FRENCH SUBMARINE Circé : World War I: The Circé-class submarine was sunk in the Adriatic Sea (41.65°N, 19.41667°W) by SMU U-47 (Austria-Hungary) with the loss of all but one of her crew.
 * Dragonos (🇬🇷 Greece): World War I: The sailing vessel was sunk in the Mediterranean Sea (36.98333°N, 21.98333°W) by SMU U-27 (Austria-Hungary) . Her crew survived.
 * SS Igor (🇸🇪 Sweden): The cargo ship sprang a leak and sank.
 * Kingfisher (🇺🇸 United States): World War I: The trawler was sunk in the Atlantic Ocean 85 nmi off Halifax, Nova Scotia, Canada (43.51667°N, -61.88333°W) by SMU U-155 . Her crew survived.
 * Prof. Elias (🇬🇷 Greece): World War I: The sailing vessel was sunk in the Mediterranean Sea (36.7°N, 22.2°W) by SMU U-27 (Austria-Hungary) . Her crew survived.
 * San Michele ( undefined): World War I: The sailing vessel was sunk in the Mediterranean Sea off Sicily by SMU UB-105.
 * Theologos (🇬🇷 Greece): World War I: The sailing vessel was sunk in the Mediterranean Sea (36.95°N, 22.08333°W) by SMU U-27 (Austria-Hungary) . Her crew survived.

21 September

 * SS Downshire (1905) ( undefined): World War I: The coaster was shelled and sunk in the Irish Sea 8 nmi west of Rockabill by SMU UB-64 . Her crew survived.
 * Santo Fortunato ( undefined): World War I: The sailing vessel was sunk in the Mediterranean Sea off Sicily by SMU UB-105.
 * SS Staithes (1883) ( undefined): The coaster was torpedoed and sunk in the North Sea 1.5 nmi south east by south of Sunderland, County Durham by SMU UB-115 with the loss of four of her crew.

22 September

 * HMT Elise : World War I: The naval trawler was torpedoed and sunk in the North Sea 2 nmi north east of St. Mary's Lighthouse, Northumberland (55.1°N, -1.45°W) by SMU UB-34 with the loss of fourteen of her crew.
 * Euthamia ( undefined): World War I: The trawler strucke a mine and sank in the North Sea 6 nmi east by north of the Humber Lightship ( undefined).
 * Gaia (🇵🇹 Portugal): World War I: The sailing vessel was sunk in the Atlantic Ocean off the Azores (37.21667°N, -23.31667°W) by SMU U-157.
 * SS Gorsemore (1899) ( undefined): World War I: The collier was torpedoed and sunk in the Mediterranean Sea 44 nmi south east of Cape Colonne, Italy (38.46667°N, 17.85°W) by SMU UC-53 . Her crew survived.
 * SS Polesley (1905) ( undefined): World War I: The cargo ship was torpedoed and sunk in the Atlantic Ocean 1 nmi north of the Pendeen Lighthouse, Cornwall (50.21667°N, -4.76667°W) by SMU UB-88 with the loss of 43 of her crew.

23 September

 * SS Aldershot (1897) ( undefined): World War I: The cargo ship was torpedoed and sunk in the English Channel 5 nmi east south east of Dartmouth, Devon by SMU UB-104 or SMU UB-113 (both ) with the loss of a crew member.
 * SS Edlington (1913) ( undefined): World War I: The cargo ship was torpedoed and sunk in the Mediterranean Sea 70 nmi east by south of Cape Passaro, Sicily, Italy (36.7°N, 16.61667°W) by SMU UC-54 . Her crew survived.

24 September

 *  Erik (🇸🇪 Sweden): The schooner sprang a leak and sank in the Atlantic Ocean off Huelva, Andalusia, Spain. Her crew were rescued by two Spanish merchant vessels.

25 September

 * Gloire a Jesus (🇫🇷 France): World War I: The sailing vessel was sunk in the Atlantic Ocean approximately 200 nmi south west of the Isles of Scilly, United Kingdom by SMU U-46.
 * SS Hebburn (1908) ( undefined): World War I: The collier was torpedoed and sunk in the Atlantic Ocean 14 nmi off Mine Head, Cornwall (51.66667°N, -7.21667°W) by SMU UB-91 with the loss of six of her crew.
 * SS Shitomu Maru (🇯🇵 Japan): The cargo ship sank at Shinagawa, Tokyo.
 * SMU U-156 : World War I: The Type U 151 submarine struck a mine and sank in the North Sea with the loss of all 77 crew.

26 September

 *  Belle Brice (🇫🇷 France): The schooner foundered in a gale at Castellón de la Plana, Spain.
 * SS Paul (🇧🇪 Belgium): World War I: The coaster was torpedoed and sunk in the North Sea off Robin Hood's Bay, Yorkshire, United Kingdom (54.45°N, -0.5°W) by SMU UB-21 . Her crew survived.
 * USS Tampa (1912) : World War I: Convoy HG 107: The Ungula-class cutter was torpedoed and sunk in the Bristol Channel 50.66667°N, -6.31667°W by SMU UB-91 with the loss of all 131 people on board.

27 September

 * En Avant (🇫🇷 France): World War I: The sailing vessel was sunk in the Atlantic Ocean 45 nmi north of Ouessant, Finistère by SMU U-54.
 * SS Hatasu (1917) ( undefined): World War I: The cargo ship was torpedoed and sunk in the Mediterranean Sea 50 nmi north by west of Oran, Algeria (36.53333°N, -0.88333°W) by SMU UB-49 with the loss of two of her crew.

28 September

 * SS Baldersby (1913) ( undefined): World War I: The cargo ship was torpedoed and sunk in the Irish Sea 9 nmi east of the Codling Bank Lightship ( undefined) by SMU UB-91 with the loss of two of her crew.
 * Benha (🇪🇬 Egypt): World War I: The sailing vessel was shelled and sunk in the Mediterranean Sea off Ras el Dabas by an enemy submarine.

29 September

 * SS Libourne (1918) ( undefined): World War I: The cargo ship was torpedoed and sunk in the English Channel 10 nmi south of The Lizard, Cornwall (49.78333°N, -5.16667°W) by SMU U-54  with the loss of three crew.
 * USS Minnesota (BB-22) : World War I: The struck a mine in the Atlantic Ocean 20 nmi off the Fenwick Island Lighthouse, Delaware and was severely damaged. She was subsequently repaired and returned to service.
 * HMML 247 : the motor launch was lost on this date.
 * SS Nyanza (1897) ( undefined): World War I: The cargo ship was torpedoed and sunk in the Irish Sea 10 nmi north west by west of the Corsewall Lighthouse, Wigtownshire by SMU UB-95 with the loss of thirteen of her crew.
 * SMU UB-115 : World War I: The Type UB III submarine was depth charged and sunk in the North Sea 4.5 nmi off Newton-by-the-Sea, Northumberland, United Kingdom (55.21667°N, 1.36667°W by HMS Ouse, HMS Star (1896), HMT Viola (all ) and the R23X-class airship R27  with the loss of all 39 crew.

30 September

 *  Atlantico (🇵🇹 Portugal): World War I: The barque was shelled and sunk in the Atlantic Ocean 6 nmi west of the Bishop Rock, Isles of Scilly, United Kingdom (49.83333°N, -6.58333°W) by SMU UB-112.
 * Francesco Padre ( undefined): World War I: The sailing vessel was sunk in the Gulf of Salerno by SMU UC-53.
 * Gabriela Costela ( undefined): World War I: The sailing vessel was sunk in the Gulf of Salerno by SMU UC-53.
 * Giovanni Costa ( undefined): World War I: The sailing vessel was sunk in the Gulf of Salerno by SMU UC-53.
 * San Francesco P. ( undefined): World War I: The sailing vessel was sunk in the Gulf of Salerno by SMU UC-53.
 * HMS Seagull (1889) : The converted Sharpshooter-class torpedo gunboat colided with another vessel and sank in the River Clyde.
 * HMT Sealark II (: The naval trawler collided with another vessel and sank off St' John's Point, County Donegal.
 * USS Ticonderoga (1918) : World War I: The transport ship was sunk in the Atlantic Ocean (43.08333°N, -38.71667°W) by SMU U-152 with the loss of 213 of the 237 people on board. Two of the survivors were taken as prisoners of war, the rest were rescued by SS Moorish Prince ( undefined).
 * SMU U-102 : World War I: The Type U 57 submarine struck a mine and sank in the North Sea east of the Orkney Islands, United Kingdom with the loss of all 42 crew.
 * SMU UB-127 : World War I: The Type UB III submarine struck a mine and sank in the Atlantic Ocean south of Fair Isle, United Kingdom with the loss of all 34 crew.

Unknown date

 * SMU UB-104 : World War I: The Type UB III submarine was lost in Lyme Bay on or after 17 September with the loss of all 36 crew.