Imperator totius Hispaniae is a Latin title meaning "Emperor of all Spain". In Spain in the Middle Ages, the title "emperor" (from Latin imperator) was used under a variety of circumstances from the ninth century onwards, but its usage peaked, as a formal and practical title, between 1086 and 1157. It was primarily used by the Kings of León and Castile, but it also found currency in the Kingdom of Navarre and was employed by the Counts of Castile and at least one Duke of Galicia. It signalled at various points the king's equality with the Byzantine Emperor and Holy Roman Emperor, his rule by conquest or military superiority, his rule over several people groups ethnic or religious, and his claim to suzerainty over the other kings of the peninsula, both Christian and Muslim. The use of the imperial title received scant recognition outside of Spain and it had become largely forgotten by the thirteenth century.
The analogous feminine title, "empress" (Latin imperatrix), was less frequently used and in only a handful of cases did it refer to a queen regnant and not a consort of the emperor.