One of three surviving rebel leaders who still bore the title "Commander of the Revolution," Almeida was a major figure in the battle to overthrow Cuban dictator Fulgencio Batista, and through the early years after the Jan. 1, 1959, triumph of the revolution.
His death "is a reminder of what everyone knows, which is that the original generation is in its final laps," said Phil Peters, a Cuba expert at the Washington-area think tank the Lexington Institute.
Almeida served in several military posts after the overthrow of Batista and was often seen at public events in uniform alongside Castro until the Cuban leader fell gravely ill in 2006 and finally resigned the presidency in 2008.
Although Almeida had also cut back on work in recent years, he was a mainstay at public events beside Castro's younger brother and successor, President Raul Castro.
Almeida joined the fight against Batista's dictatorship in March 1952 as a young law student at the University of Havana, where he met Fidel Castro, another aspiring attorney.
Almeida was at Castro's side July 26, 1953, when Castro led an armed attack on the Moncada, a military barracks in Santiago. It was a disaster, and Almeida and both Castros were sent to prison. But that failure launched the revolutionary battle that triumphed 5 1/2 years later.
His military exploits earned him the title "Comandante de la Revolucion," reserved for top leaders of rebel troops under Fidel Castro's command in the 1950s. Now only Ramiro Valdes and Guillermo Garcia hold the distinction.
Almeida was a highly visible member of Cuba's ruling elite. He sat on the Communist Party's politburo and served as a vice president on the Council of State, the country's supreme governing body.
Almeida, born Feb. 17, 1927, in Havana, was a bricklayer who began working at age 11. He also composed traditional Cuban music. It was not clear how many survivors he had.