The Type UB I was a class of small coastal submarines (U-boats) built in Germany at the beginning of the First World War. Twenty boats were constructed, most of which went into service with the German Imperial Navy. Boats of this design were also operated by the Austro-Hungarian Navy (Kaiserliche und Königliche Kriegsmarine or K.u.K. Kriegsmarine) and the Bulgarian Navy. The group is sometimes known as the UB-1 class after , the class leader. In the Austro-Hungarian Navy, it was called the U-10 class.