SM U-1 or U-I was the lead boat of the U-1-class of submarines or U-boats built for and operated by the Austro-Hungarian Navy. U-1 was designed by American naval architect Simon Lake of the Lake Torpedo Boat Company, and constructed at the Navy Yard in Pola. She was one of two Lake-designed submarines purchased as part of a competitive evaluation of foreign submarine designs after domestic proposals were rejected by the Navy.

The U-1 class was a class of two submarines or U-boats built for and operated by the Austro-Hungarian Navy. The class comprised U-1 and U-2. The boats were built to an American design at the Pola Navy Yard after domestic design proposals failed to impress the Navy. Constructed between 1907 and 1909, the class was a part of the Austro-Hungarian Navy's efforts to competitively evaluate three foreign submarine designs.