Emperor Antoku (December 22, 1178 – April 24, 1185) was the 81st emperor of Japan, according to the traditional order of succession. His reign spanned the years from 1180 through 1185.
Antoku was named crown prince at around one month of age. He ascended the throne at one year of age. Naturally, he held no actual power, but rather his grandfather Taira no Kiyomori ruled in his name, though not officially, as sesshou (regent).
In the year of 1180 (the 12th year of Takakura-tennou's reign), the emperor was forced to abdicate; and the succession was received by his infant son, the grandson of Taira Kiyomori. Shortly thereafter, Emperor Antoku is said to have acceded to the throne. In the year of his enthronement, the capital was moved to modern-day Kobe, Hyogo, but it was soon moved back to Heian-kyo.
In 1183, Go-Toba is proclaimed emperor by the Genji; and consequently, there were two proclaimed emperors, one living in Heian-kyo and another in flight towards the south. When Minamoto no Yoshinaka entered the capital, the Taira clan fled with the young emperor and the sacred treasures to Yashima. Being defeated in the Battle of Yashima, they fled westward.
In 1185, The Taira and the Minamoto clashed in the Battle of Dan-no-ura. The Taira were defeated. Antoku's grandmother, Taira no Tokiko, the widow of Taira no Kiyomori, drowned herself along with the young emperor. His mother also drowned herself, but apparently, according to the The Tale of the Heike (Heike Monogatari), she was pulled out with a rake by her long hair. According to legend, the sacred jewels and the sacred sword (two of the three sacred treasures) sunk to the bottom of the sea, and although the sacred jewels were recovered, the sword was lost.
The story of Emperor Antoku and his mother's family became the subject of the Kamakura period epic poem The Tale of the Heike.