Ms Tajima, who became the oldest woman in Japan in September 2015, could have been the world's oldest person since Ms Violet Brown of Jamaica died in September previous year at age 117, Japanese media said.
Ms Tajima was born on August 4, 1900, and reportedly had more than 160 descendants, including great-great-great grandchildren.
Tajima, who became the world's oldest known person with the death of Jamaican Violet Brown on September 15, seems to have paperwork on her side.
Nabi Tajima died of old age in a hospital Saturday evening in the town of Kikai in southern Japan, town official Susumu Yoshiyuki confirmed.
She had been hospitalised in the town of Kikai since January.
The world's oldest person, who has died in Japan aged 117, was born five years before Japan's victory in the Russo-Japanese war, marking the start of the modern era in the country. Miyako will turn 117 on May 2, according to the Gerontology Research Group.
Chiyo Miyako, a resident of Yokohama near Tokyo, is now the world's oldest living person.
There are around 68,000 people aged 100 or older in the country, the government said past year.
Mrs Tajima's death comes just days after Chilean man Celino Villanueva Jaramillo died at the age of 121 after piercing a lung when he fell out of bed. At 116 years and 355 days, she has about nine months to reach her countrywoman's mark of 117 years and 260 days.