SM UB-100 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 17 September 1918 as SM UB-100.
UB-100 was surrendered on 22 November 1918 and broken up in Dortrecht in 1922.
She was built by AG Vulcan of Hamburg and following just under a year of construction, launched at Hamburg on 13 August 1918. UB-100 was commissioned later the same year . Like all Type UB III submarines, UB-100 carried 10 torpedoes and was armed with a deck gun. UB-100 would carry a crew of up to 3 officer and 31 men and had a cruising range of . UB-100 had a displacement of while surfaced and when submerged. Her engines enabled her to travel at when surfaced and when submerged.