SM UB-107 was a German Type UB III submarine or U-boat in the German Imperial Navy () during World War I. She was commissioned into the German Imperial Navy on 16 February 1918 as SM UB-107.
The submarine conducted 4 patrols and sank 11 ships during the war for a total loss of . UB-107 was sunk on 27 July 1918 by and HMT Calvis at .
UB-107 was ordered by the GIN on 23 September 1916. She was built by Blohm & Voss of Hamburg and following just under a year of construction, launched at Hamburg on 21 July 1917. UB-107 was commissioned early the next year . Like all Type UB III submarines, UB-107 carried 10 torpedoes and was armed with a deck gun. UB-107 would carry a crew of up to 3 officer and 31 men and had a cruising range of . UB-107 had a displacement of while surfaced and when submerged. Her engines enabled her to travel at when surfaced and when submerged.
The first recorded fate of UB-107 was noted as sunk by depth charge on 27 July 1918 by the Royal Navy trawler Calvia and destroyer Vanessa at position . It has since been argued that the UB-107 was probably not present for the attack by Calvis and Vanessa as it was the only U-boat that could have been responsible for the sinking of steamers Chloris and John Rettig two and a half hours later at position .
In 1985 divers discovered the wreck of UB-107 one mile north of Flamborough Head at position entangled with another wreck, the , a British steamer torpedoed and sunk on 3 August 1918 reported as being by , though UB-104's record says it was not in the area nor that it attacked a ship on that day. UB-107 was identified by the markings on her propellers. It is suggested that either UB-107 suffered an accident of some sort or was lost on a British mine between 28 July and 3 August 1918, leaving all hands lost (38 dead).
The fate of UB-107 was the subject of an episode of the documentary television series Deep Sea Detectives: "Mystery U-Boat of WWI". The documentary offered various scenarios for the sinking based on historical evidence and exploratory diving at the wreck site.