U 31

U 31 denotes:

• SM U 31 , a submarine of the German Imperial Navy
• SM U 31 , a submarine of the Austro-Hungarian Navy, see SM Unterseeboote #SM U 27, U 28, U 29, U 30, U 31, U 32, U 40, U 41, U 43, U 47
• U 31 (Kriegsmarine) , a submarine of the German Kriegsmarine
• U 31 (Bundeswehr) , a submarine of the German Navy

This is a disambiguation page for differentiating between several terms identified with the same word.