U-12 or U-XII may refer to:

• {{ship|German submarine|U-12}}, any one of several German submarines
• {{SMS|U-12|Austria-Hungary|sub=y}}, a U-5-class submarine of the Austro-Hungarian Navy

• 1952 Venezuelan Constituent Assembly election
• 1952 VFL Grand Final
• 1952 VFL Lightning Premiership
• 1952 Vincent Black Lightning
• 1952 Wake Forest Demon Deacons football team
• 1952 Washington D C UFO incident
• 1952 Washington D. C. UFO incident
• 1952 Washington Huskies football team
• 1952 Washington Redskins season
• 1952 Waterford by-election
• 1952 Werriwa by-election
• 1952 West Bengal Legislative Assembly election
• 1952 Wilkes County 200
• 1952 William & Mary Indians football team
• 1952 William & Mary Tribe football team
• 1952 Wimbledon Championships - Men's Singles
• 1952 Wimbledon Championships - Women's Singles
• 1952 Winter Olympics medal count
• 1952 Wisconsin Badgers football team
• 1952 World Fencing Championships
• 1952 World Figure Skating Championships
• 1952 World Professional Match-play Championship
• 1952 World Snooker Championship
• 1952 WS
• 1952 Úrvalsdeild