Twelfth can mean:
- The Twelfth Amendment to the United States Constitution
- The Twelfth, a Protestant celebration originating in Ireland
- Twelfth of the month, a recurring calendar date
- Twelfth grade, in education
Mathematics
- 12th, an ordinal number; as in the item in an order twelve places from the beginning, following the eleventh and preceding the thirteenth
- , a vulgar fraction, one part of a unit divided equally into twelve parts
Music
- The note twelve scale degrees from the root (current note, in a chord)
- Twelfth (interval)
Currency
- Uncia (coin), a Roman coin worth 12th of an As
Geography
- 12th meridian east, a line of longitude
- 12th meridian west, a line of longitude
- 12th parallel north, a circle of latitude
- 12th parallel south, a circle of latitude
- 12th Avenue (disambiguation)
- 12th Street (disambiguation)
Military
- 12th Army (disambiguation)
- 12th Battalion (disambiguation)
- 12th Brigade (disambiguation)
- 12th Division (disambiguation)
- 12th Regiment (disambiguation)
- 12th Squadron (disambiguation)
See also
- 12 (number)
- 12th century
- 12th century BC
- Twelfth Amendment (disambiguation)
- Eleventh (disambiguation)
- Thirteenth (disambiguation)