Pollan, who was hospitalized several days ago for a respiratory complication, died of a heart attack Friday at Calixto Garcia Hospital, daughter Laura Maria Pollan told CNN.
Pollan helped found Ladies in White after her husband, Hector Maseda, and 74 other dissidents were arrested in a March 2003 crackdown known as Black Spring. All the dissidents were freed, most after a deal last year between the Catholic Church and President Raul Castro.
Pollan and family members of the other prisoners held silent marches every Sunday to pressure the government for the dissidents' release. They dressed in white and each carried a white flower while walking along a street after attending mass at a Catholic church.
The Daily Telegraph reported Elizardo Sanchez, head of the independent Cuban Commission of Human Rights, called Pollan's death a major loss for opponents of the Cuban government.
"It's really bad news for the human rights and pro-democracy movement. It's an irreparable loss. We'll see with time if others step forward to take her place," he said.
The government tried to stop the protests, then unheard of in Communist Cuba, but allowed them after the church intervened.
Pollan's husband said a wake would be held at their home in Central Havana and her body would be cremated. Her ashes would be spread in a field of flowers, as she had requested, he said.