Itoku, which means "Splendid Benevolence," is the name traditionally given to the mythical 4th emperor of Japan, according to the traditional chronology, a figure who is said to have lived from 553 to 477 BC, reigning from 510 until his death.
Itoku is listed as the 4th emperor in the 8th century historical chronicle Nihon Shoki (the oldest written Japanese historical chronicle), but other than his name and dates, nothing else is said about him. The same is the case with the other emperors after the second and before the eleventh, so collectively these eight unexplicated emperors are known in Japanese as the "eight undocumented monarchs" (欠史八代, kesshi hachidai, literally "eight reigns with no history").
In general, Itoku is presumed to be a son of Emperor Annei, another undocumented emperor who is listed as preceding him, and later chroniclers made this assumption explicit.
The Japanese have traditionally accepted Itoku as a real monarch who really existed, but modern historians have found no evidence of this, and a variety severe chronology problems with the early emperors make it unlikely that any figure with this name ever existed anywhere near the time he is supposed to have existed (for one thing, Japan was inhabited by hunter-gatherers at that time and lacked even the barest semblance of a centralized state).
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