Maria Gomes Valentim died of multiple organ failure, said Helerson Lima, a spokesman for the nursing home where she lived. Valentim would have turned 115 on July 9.
Guinness said Tuesday on its website that Valentim, "the first Brazilian super-centenarian to hold the title," died at the age of 114 years, 347 days.
On May 18, Guinness determined that Valentim was 48 days older than the person previously considered the world's oldest human, Besse Cooper from Monroe, Georgia.
"With Maria's passing, the title of Oldest Living Person reverts back to American Besse Cooper, age 114 years 299 days," Guinness said.
The Georgia woman's son, Sid Cooper, said Tuesday that his mother is doing well at her Monroe retirement community.
"She's gained some weight, she's eating real good," Sid Cooper said.
"Her memory is still really good," he added. "She remembers things from a long time ago and recognizes people."
Guinness verified that Valentim was born on July 9, 1896, in the city of Carangola in the southeastern state of Minas Gerais. She lived there all her life.
Last month, Guinness said on its website that Valentim, who was known as "Grandma Quita," attributed her longevity to a healthy diet: eating a roll of bread every morning with coffee, fruit and the occasional milk with linseed.
Valentim's family told reporters that she had a stubborn streak and always made a habit of minding her own business. They also said that her father lived to be 100.
"She says she has lived long because she has always taken care of her own life - and not meddled in the lives of others," granddaughter Jane Ribeiro Moraes, 63, told a local newspaper in May.
Valentim married her husband, Joao, in 1913. He died in 1946.
Valentim is survived by four grandchildren, seven great-grandchildren and five great-great grandchildren. Her only son died at age 75 in the early 1990s.
Valentim was scheduled to be buried Tuesday afternoon at the Carangola cemetery.