The word emperor can mean the male ruler of an empire. Empress, the female equivalent, may indicate an emperor's wife, mother/grandmother, or a woman who rules in her own right and name. Emperors are generally recognized to be of the highest monarchic honour and rank, surpassing kings. In Europe, the title of Emperor has been used since the Middle Ages, considered in those times equal or almost equal in dignity to that of Pope due to the latter's position as visible head of the Church and spiritual leader of the Catholic part of Western Europe. The emperor of Japan is the only currently reigning monarch whose title is translated into English as "Emperor".

सम्राट हा अनेक राज्ये जिंकून व सामील करून बनलेल्या मोठ्या सार्वभौम साम्राज्याचा शासक असतो. सम्राटांना राजा-महाराजांपेक्षा उच्च प्रतिष्ठा असते.