SM U-3 or U-III was the lead boat of the U-3 class of submarines or U-boats built for and operated by the Austro-Hungarian Navy (German: Kaiserliche und Königliche Kriegsmarine or K.u.K. Kriegsmarine) before and during the First World War. The submarine was built as part of a plan to evaluate foreign submarine designs, and was built by Germaniawerft of Kiel, Germany.