SM U-3 was the third German U-Boat created by the German Empire in their history, and the first of two submarines in its class. The boat was built by Kaiserliche Werft Danzig and was launched on March 27, 1909. U-3 began its career in World War I as a training boat from August 1, 1914 to November 11, 1918. On December 1, 1918, the surrendered boat was being towed to Preston to be broken up when it sank. Unlike the first two U-boat designs, the third design was fitted with a SK L/40 deck gun.