Records of heads of state
Officially, the current Emperor of Japan, Akihito is the 125th in line from the first emperor Jimmu, who is variously believed to have reigned in the 1st or 7th century BC. The earliest documentary evidence is only for the 29th emperor, Kinmei (AD 509–571); however, this is sufficient such that even the most conservative of estimates still places the Japanese imperial family as among the oldest lines in the world today.
Emperor of Japan
There are two Japanese words equivalent to the English word "Emperor": "tennō" (, "heavenly sovereign"), which is used exclusively to refer to the Emperor of Japan, and "kōtei" (皇帝, the title used for all other foreign Emperors), which is used primarily to describe non-Japanese Emperors. "Sumeramikoto" ("the Imperial person") was also used in Old Japanese. The term "tennō" was used by the Emperors up until the Middle Ages; then, following a period of disuse, it was used again from the 19th century. In English, the term "mikado" ( or ), literally meaning "the honorable gate" (i.e. the gate of the imperial palace, which indicates the person who lives in and possesses the palace), was once used (as in "The Mikado", a 19th-century operetta), but this term is now obsolete. (Compare Sublime Porte, an old term for the Ottoman government.)