U12
U12 may refer to:

Submarines 
 , various vessels
 , a submarine of the Austro-Hungarian Navy

Other uses 
 U12 (Berlin U-Bahn), a former railway line
 "U12" (song), a 2015 song by Daya
 Nissan Bluebird (U12), a Japanese sedan
 Nissan Pintara (U12), a Japanese sedan
 Snub cube
 U12 Consortium, a university alliance in Taiwan
 U12 minor spliceosomal RNA
 Udet U 12 Flamingo, a German biplane
 BMW X1 (U12), a German crossover exclusively sold in China
 Under-12, an age classification in many youth sports