U31

U31 may refer to:

Naval vessels

 * BRAZILIAN DESTROYER ESCORT Bracuí
 * GERMAN SUBMARINE U-31, various vessels
 * SM U-31, a submarine of the Austro-Hungarian Navy

Other uses

 * Nissan Presage (U31), a Japanese minivan
 * Small icosicosidodecahedron
 * Small nucleolar RNA SNORD31