The U-43 class was a class of two coastal submarines or U-boats operated by the Austro-Hungarian Navy (German: Kaiserliche und Königliche Kriegsmarine or K.u.K. Kriegsmarine) during World War I. The two submarines that comprised the class were Type UB II submarines of the Imperial German Navy, making the two classes identical. From the beginning of World War I, Austria-Hungary had been working to increase the size of its U-boat fleet, so the Imperial German Navy, which was finding it difficult to obtain trained submarine crews, sold two of its UB II boats, UB-43 and UB-47, to its ally in June 1917.