Empress Genshō

Empress Genshō (683 – May 22, 748) was the 44th monarch of Japan, according to the traditional order of succession. Genshō ruled during the years 715 to 724.
In the history of Japan, Genshō was the fifth of eight women to take on the role of empress regnant, meaning that she was the ruler in her own right and not a ruler because she was a married to a ruler. 
Genshō was the only Japanese empress regnant to get her title from another empress regnant, rather than a previous male ruler.