SM UC-23 was a German Type UC II minelaying submarine or U-boat in the German Imperial Navy () during World War I. The U-boat was ordered on 29 August 1915 and was launched on 29 February 1916. She was commissioned into the German Imperial Navy on 17 July 1916 as SM UC-23."SM" stands for "Seiner Majestät" () and combined with the U for Unterseeboot would be translated as His Majesty's Submarine. In 17 patrols UC-23 was credited with sinking 46 ships, either by torpedo or by mines laid. UC-23 was surrendered at Sevastopol on 25 November 1918 and broken up at Bizerta in August 1921.
Design Like all pre-UC-25 Type UC II submarines, UC-23 had a displacement of when at the surface and while submerged. She had a length overall of , a beam of , and a draught of . The submarine was powered by two six-cylinder four-stroke diesel engines each producing (a total of ), two electric motors producing , and two propeller shafts. She had a dive time of 35 seconds and was capable of operating at a depth of .
The submarine had a maximum surface speed of and a submerged speed of . When submerged, she could operate for at ; when surfaced, she could travel at . UC-23 was fitted with six mine tubes, eighteen UC 200 mines, three torpedo tubes (one on the stern and two on the bow), seven torpedoes, and one Uk L/30 deck gun. Her complement was twenty-six crew members.
Summary of raiding history DateNameNationalityTonnageMerchant ship tonnages are in gross register tons. Military vessels are listed by tons displacement.Fate29 November 1916Minnewaska14,317Sunk31 December 1916Venus281Sunk21 February 1917HMS Princess Alberta1,586Sunk10 June 1917Kleopatra160Sunk13 June 1917Aghios Nicolaos120Sunk14 June 1917New Zealand Transport4,481Sunk18 June 1917Pannomitis11Sunk18 June 1917Xiphias483Sunk19 June 1917Jakobus304Sunk19 June 1917Maria35Sunk19 June 1917Raxiarchos30Sunk2 August 1917HMS Ermine1,777Sunk6 September 1917HMT Helgian220Sunk7 September 1917HMT By George225Sunk21 September 1917Santo Nicola159Sunk21 September 1917Spiridon128Sunk23 September 1917Nicolaos104Sunk19 January 1918Trocas4,129Sunk22 January 1918Evangelistria21Sunk23 January 1918Birkhall4,541Sunk24 January 1918Aghia Arene16Sunk24 January 1918Aghios Johannes14Sunk20 February 1918Hagios Nicolaos18Sunk20 February 1918Maria Archis13Sunk20 February 1918Taxi Arches3Sunk23 February 1918Aspasia105Sunk28 February 1918Hagios Triast22Sunk11 April 1918Trud610Captured as prize14 April 1918Unidentified lighter100Sunk14 April 1918Kazak622Captured as prize14 April 1918Olga327Captured as prize15 April 1918Rostov1,280Sunk3 October 1918Blasios181Sunk3 October 1918Evangelistria35Damaged5 October 1918Hagios Marcos45Sunk5 October 1918Maria2,159Sunk5 October 1918Marigo48Sunk5 October 1918Reventazon4,050Sunk13 October 1918Aghion Spiridon21Sunk13 October 1918Aghios Georgios130Sunk13 October 1918Biolleta99Sunk13 October 1918Evangelistria41Sunk13 October 1918Evangelistrios121Sunk13 October 1918Glaros43Sunk13 October 1918Iphigenia75Sunk13 October 1918Panaghia26Sunk13 October 1918Urania23Sunk15 October 1918Evangelistria24Sunk15 October 1918Georgios29Sunk15 October 1918Maria43Sunk
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