Walther Forstmann (March 9, 1883 – November 2, 1973) was one of the most successful and highly decorated U-boat commanders in the Kaiserliche Marine during World War I. He also served in the Kriegsmarine during World War II in different staff positions.In his time as commander of U-12 and U-39 in World War I, he conducted 47 patrols and succeeded in sinking 146 ships for a total tonnage of 384,304 gross register tons (GRT).