Celeste Caeiro, who on April 25, 1974, handed out red carnations to soldiers on their way to ending a 40-year right-wing dictatorship in Portugal, a spontaneous patriotic act that gave a largely bloodless coup its name, the Carnation Revolution, and her an enduring appellation, “the Lady of the Carnations,” died on Friday in Lisbon. She was 91.

Her granddaughter, Carolina Caeiro Fontela, confirmed her death, in a hospital, to Portugal’s national news agency, Lusa. She said Ms. Caeiro had a history of heart and lung problems.

Ms. Caeiro was a 40-year-old single mother and a cloakroom attendant at a Lisbon restaurant called Sir when she showed up for work that April morning expecting a busy day; it was the restaurant’s first anniversary, and her boss had prepared a special lunch and dinner menu, with red and white carnations on every table.

But since dawn he had been listening to a private radio station — one that had evaded the dictatorship’s censors — and when she arrived he told her that he was closing the restaurant, saying, “Something’s going on.” He told her to take the carnations home. “We don’t want them to go to waste,” he said.

On her way home, Ms. Caeiro saw a column of army tanks and armored personnel carriers rumbling toward her, flanked by infantrymen. Lisbon residents were streaming from their homes to greet them with Portuguese flags. She was told that the soldiers, led by a group of dissident young captains calling themselves the Armed Forces Movement, were determined to oust the dictatorial prime minister, Marcelo Caetano, and his loyal generals.

The officers’s main grievance was the government’s continuing wars against independence movements in colonial Africa, where many if not most poor Portuguese families had lost loved ones in the fighting. The unrest had cost Portugal some 40 percent of its national budget, inflicting hardships on its people.