Cuban political prisoner Orlando Zapata Tamayo has died in hospital after 85 days on hunger strike.
Mr Zapata, 42, had been transferred to a Havana hospital from a smaller clinic in the central province of Camaguey after his condition worsened on Monday.
Amnesty International declared him a prisoner of conscience after his arrest in March 2003 in a crackdown on opposition groups.
He had been refusing food in protest at jail conditions.
Mr Zapata, whose family announced last week that he was seriously ill, died on Tuesday in Havana's Hermanos Ameijeiras hospital.
His death marks the first time in nearly 40 years a Cuban activist starved himself to death to protest against government abuses.
The last political prisoner to die on hunger strike in Cuba was Pedro Luis Boitel, a poet and student leader, in 1972.
Mr Zapata's mother, Reina Luisa Tamayo, told the Miami newspaper El Nuevo Herald by telephone that her son had been "murdered" by Cuba's authorities.
"They managed to do what they wanted," she said. "They ended the life of a fighter for human rights.''
Laura Pollan, a dissident from the group known as Ladies in White, told the BBC: "He wasn't a murderer. He wasn't a thief. He wasn't a rapist. He was simply a young man who wanted a better future for Cuba."
Mr Zapata was among a group of some 75 dissidents jailed by the authorities in 2003. He was initially sentenced to three years in prison, but this was increased to 25 years in subsequent trials.
Cuba's illegal but tolerated Human Rights Commission says there are about 200 political prisoners still held in Cuba, about one-third less than when Raul Castro took over as president from his brother Fidel.
But if anything harassment of dissidents has increased over the past year, the group says.
Cuba designates prisoners of conscience as mercenaries sympathetic to the United States.