SM U-28 or U-XXVIII was a U-27-class U-boat or submarine for the Austro-Hungarian Navy. U-28, built by the Austrian firm of Cantiere Navale Triestino (CNT) at the Pola Navy Yard, was launched in January 1917 and commissioned in June. During her service career, U-28 sank the British Q-ship HMS and nine other ships, sending a combined tonnage of 44,743 to the bottom. U-28 was surrendered at Venice in 1919, granted to Italy as a war reparation and broken up the following year.