Akihito to become first Japanese Emperor to abdicate in 200 years.
This decision was taken on Frtiday at a meeting of the Imperial House Council and announced by Japan's PM Shinzo Abe.
"I will do my upmost to ensure that the Emperor's abdication and the ascension of the Crown Prince will proceed smoothly with the blessing of all of our citizens," Abe said.
His abdication will mark the end of the Heisei era, and he would be immediately succeeded by his son Crown Prince Naruhito on 1 May, which would start a new imperial era.
In a rare address to the nation last year, Akihito said he was "worried that it may become difficult for me to carry out my duties" with his declining fitness, and expressed concern for the strain imposed on his family and Japanese society if he fell ill and died while on the throne.
His statement was widely interpreted as a wish for abdication, which at the time was not provided for under the law.