SM UB-43 was a Type UB II submarine or U-boat for the German Imperial Navy (German: Kaiserliche Marine) during World War I. UB-43 was sold to the Austro-Hungarian Navy (German: Kaiserliche und Königliche Kriegsmarine or K.u.K. Kriegsmarine) during the war. In Austro-Hungarian service the B was dropped from her name and she was known as SM U-43 or U-XLIII as the lead boat of the Austro-Hungarian U-43 class.