Empress Kogyoku (皇極天皇) or Saimei (斉明天皇) ( 594- 661) was the 35th imperial ruler of Japan. From 642 she ruled as Kogyoku, but abdicted in favour of her son Kotoku in 645. After her son died in 655, she reascended the throne as Saimei, and ruled under that name until her death.