R.
R. or r. may refer to:Reign, the period of time during which an Emperor, king, queen, etc., is ruler
- Rex or regina, abbreviated as R., the Latin words meaning "King" and "Queen", respectively
- * Commonly used for criminal prosecution in Commonwealth realms where offences are brought in the name of the monarch
- Regnavit or rexit, abbreviated as r., used in historiography to designate the ruling period of a person in dynastic power, to distinguish from his or her lifespan R., an album by American singer R. Kelly