SM U-139

SM U-139 was a German U-boat of the Type U 139 class, also known as the U-Kreuzer class, built for the Kaiserliche Marine (Imperial German Navy) during World War I. She was one of seven such submarines commissioned, designed for long-range operations and capable of carrying a substantial amount of cargo or acting as a minelayer.

U-139 was commissioned in May 1918 under the command of Lothar von Arnauld de la Perière, a highly successful U-boat commander credited with sinking a large amount of tonnage. Under his command, and later under Johannes Spiess, U-139 primarily operated in the Atlantic, targeting Allied shipping.

Notable for her large size and heavy armament, which included two 15 cm (5.9 inch) deck guns, U-139 was a formidable opponent. She sunk several vessels during her service. However, her size also made her a more prominent target.

Following the Armistice in November 1918, U-139 surrendered to the Allies and was subsequently broken up. She represents a significant example of Germany's attempt to disrupt Allied supply lines and exert pressure during the later stages of World War I using advanced submarine technology.