R. or r. may refer to: * '' Reign'', the period of time during which an Emperor, king, queen, etc., is ruler. * '' Rex'', abbreviated as R., the Latin word meaning King * ''Regina'', abbreviated as R., the Latin word meaning Queen * or , abbreviated as r., used in historiography to designate the ruling period of a person in dynastic power, to distinguish from his or her lifespan (e.g. "Charles V (r. 1519–1556)") * Abbreviation R., meaning ''" the Crown"'' or ''" the state"'' in criminal prosecution in

Commonwealth realm A Commonwealth realm is a sovereign state in the Commonwealth of Nations whose monarch and head of state is shared among the other realms. Each realm functions as an independent state, equal with the other realms and nations of the Commonwealt ...

s (e.g. ''"R. v Defendant"'') * R., an album by American singer R. Kelly

See also