The death was announced on Cuban state TV by Castro’s younger brother, Raul, who succeeded his brother years ago as the country’s leader.

The son of a prosperous sugar planter, Mr. Castro took power in Cuba on New Year’s Day 1959 promising to share his nation’s wealth with its poorest citizens, who had suffered under the corrupt quarter-century dictatorship of Fulgencio Batista.

Mr. Castro, a romantic figure in olive-drab fatigues and combat boots, chomping monstrous cigars through a bushy black beard, became a spiritual beacon for the world’s political far left.

To his legion of followers, Mr. Castro was a hero who demanded a fair deal for the world’s poor and wasn’t afraid to point his pistol at the powerful to get it. His admirers said he educated, fed and provided health care to his own people, as well as to the poor in other countries, more fairly and generously than the world’s wealthy nations, most notably what he called the “Colossus to the North.”

He abolished Christmas as an official holiday for nearly 30 years. While he dispatched Cuban-educated doctors and Cuban-developed vaccines to the poorest corners of Latin America, Cubans in central Havana found pharmacy shelves empty of medicine, and many lived in apartments in which they used buckets in their kitchens as toilets.

Mr. Castro’s long reign began to unravel July 31, 2006, when he temporarily transferred power to his 75-year-old brother, Raúl, after undergoing what he described as intestinal surgery (the precise nature of Mr. Castro’s health problems was an official state secret). The transfer of power came just weeks before Mr. Castro’s 80th birthday on Aug. 13, and Mr. Castro was not seen in public again for nearly four years.