Maria de Jesus, who was born September 10, 1893, and was listed by the Guinness Book of World Records and the Gerontology Research Group as the world's oldest person, died in an ambulance near the town of Tomar.
The title nows falls to an American, 114-year-old Gertrude Baines, who lives in a Los Angeles nursing home.
De Jesus, who outlived three of her six children, had 11 grandchildren and 16 great-grandchildren, had eaten breakfast normally but was being taken to hospital because of a swelling, her daughter Maria Madalena told state news agency Lusa.
Corvelo Sousa, president of the town council of Tomar, 66 kilometers (40 miles) north of the port city of Porto, confirmed the death.
"I regret the death of this lady, she really was the sweetest person," said Tomar town councilor Ivo Santos.
De Jesus was left a widow when she was 57 and lived to reach 115 years and 114 days.
There are now only 82 women and nine men who have been verified through birth certificates or other records as being 110 or older, said University of California, Los Angeles, gerontologist Dr. Stephen Coles of the Gerontology Research Group, which tracks supercentenarians.
However, there could be hundreds more in China, India, Africa and elsewhere who have not come to the attention of the small volunteer group, he said.
Coles said the supercentenarians appear to share one trait that might account for their longevity -- they come from families whose members are long-lived.
"Whether they drink alcohol or not, it doesn't matter. Whether they smoke cigarettes or not doesn't seem to matter," he said. "The thing that does seem to matter is that they chose their parents wisely."
"It's in the genes. It's in the DNA," he said.
Baines, the new titleholder, was born on April 6, 1894, in Georgia. Coles said she spent most of her life in Ohio, where she worked as a dormitory housekeeper at Ohio State University in Columbus. Her only daughter died at age 18.
Coles said he asked the staff at Western Convalescent Hospital to tell Baines that she is now the oldest living documented person in the world.
"She's very healthy. Her only complaint, as far as I can tell, is arthritis in her left knee," he said. She uses a wheelchair. He described her as mentally sharp.
"She doesn't forget anything," he said.
Baines voted in the November presidential election, the Los Angeles Times reported.
She voted for Barack Obama "'cause he's for the colored people," said Baines, who is black and the daughter of former slaves.