Salima Khan, born in around 1931 and who was married at the age of 14 -- two years before the end of British colonial rule in India -- had a lifelong dream of being able to read and write.
Khan, from Bulandshahr in the northern state of Uttar Pradesh, said there were no schools in her village when she was a girl.
Six months ago, she began studying alongside pupils eight decades younger than her, and she is accompanied on her way to class by her grandson's wife.
Her story emerged after a video of her counting from one to 100 went viral on social media.
"My grandchildren used to trick me into giving them extra money as I couldn't count currency notes," she was quoted as saying by the Times of India. "Those days are gone."
India's literacy rate is around 73 percent, according to the 2011 census.
"Her story reinforces the belief that the pursuit of knowledge is not limited by age," local education officer Lakshmi Pandey told AFP.
Volunteers from a government education initiative had identified Khan as a potential student and encouraged her to go to school, Pandey said.
School headmistress Pratibha Sharma said teachers had been initially "hesitant" about embarking on teaching Khan, but were won over by her "passion" to study.
"We didn't have the heart to refuse her", Sharma told the Times of India.
Since she went to school, 25 women from her village have also started literacy classes, including two daughters-in-law, Sharma told the daily.
Guinness World Records lists the late Kimani Ng'ang'a Maruge from Kenya as the oldest person to complete primary school, having enrolled in 2004 when he was aged 84.
A former Mau Mau guerilla fighter against British colonial forces, Maruge started school wanting to count money and read the Bible, and was later appointed "senior head-boy".
