SM U-158 was a Type U-158 submarine of the Imperial German Navy, built during the First World War.SM U-158 was one of six 810-ton boats ordered in February 1917. She was one of two ships built to an improved design developed from the Type U-115 design, along with her sister, SM U-159. They were known as 'Project 25', and had a greatly increased radius of action. Both ships were built at Kaiserliche Werft Danzig, with U-158 being launched on 16 April 1918.