Ashen and grave, President Castro told the nation in an unexpected late night broadcast on state television that Fidel Castro had died and would be cremated later on Saturday.
There would now be several days of national mourning on the island.
Raul Castro ended the announcement by shouting the revolutionary slogan: “Towards victory, always!”
Barring the occasional newspaper column, Fidel Castro had essentially been retired from political life for some time, the BBC’s Will Grant in Havana reports.
In April, Fidel Castro gave a rare speech on the final day of the country’s Communist Party congress.
He acknowledged his advanced age but said Cuban communist concepts were still valid and the Cuban people “will be victorious”.
An accomplished tactician on the battlefield, he and his small army of guerrillas overthrew the military leader Fulgencio Batista in 1959 to widespread popular support.
Within two years of taking power, he declared the revolution to be Marxist-Leninist in nature and allied the island nation firmly to the Soviet Union.
Yet, despite the constant threat of a US invasion as well as the long-standing economic embargo on the island, Castro managed to maintain a communist revolution in a nation just 90 miles (145km) off the coast of Florida.
Despised by his critics as much as he was revered by his followers, he outlasted ten US presidents and defied scores of attempts on his life by the CIA.