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SM U-12 or U-XII was a U-5-class submarine or U-boat built for and operated by the Austro-Hungarian Navy before and during the First World War.

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SM U-26 was one of the 329 submarines serving in the Imperial German Navy in World War I.

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SM U-27 was a German Type U-27 U-boat built for service in the Imperial German Navy. She was launched on 14 July 1913, and commissioned on 8 May 1914 with Kapitänleutnant Bernd Wegener in command.

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SM U-28 was a Type U 27 U-boat that served in the First World War. It conducted 5 patrols, sinking 40 ships totalling 90,126 GRT.

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SM U-29 was a Type U-27 U-boat of the Imperial German Navy. She served during the First World War.

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SM U-35 was a German U 31-class U-boat which operated in the Mediterranean Sea during World War I. It ended up being the most successful U-boat participating in the war, sinking 224 merchant ships for a total of 542,047 gross register tons (GRT).

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SM U-36 was a Type 31 U-boat in the service of the Imperial German Navy of the German Empire, employed in the commerce war in World War I.

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SM U-38 was a German Type U 31 U-boat which operated in the Mediterranean Sea during World War I. It ended up being the third most successful U-boat participating in the war, sinking 138 merchant ships sunk for a total of 292,445 GRT.

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SM U-40 was a German Type U 31 U-boat of the German Imperial Navy during World War I.