Phyll Babb, 99, from Salisbury in Wiltshire, is walking one mile twice a week over the next year to raise funds for Salisbury Trust for the Homeless (STFH).
Ms Babb, who turns 100 next July, said the idea came while she was at a fundraising party for the charity.
“I thought ‘here am I having a lovely time, and still fit and healthy. I can do something to help those less fortunate than I am’,” she explained.
“I only decided to do this very recently,” said Ms Babb, who turned 99 on 13 July.
Her 45-minute walks will take her from home, round the city’s historic Cathedral Close and back again using a rollator aid.
She plans to finish the last walk by her 100th birthday.
“STFH has helped such a lot of people who have been in its houses retrain and get back to normal living,” added Ms Babb, who is a former chairman of the trust and a long-time volunteer for the charity.
Gordon Pardy, STFH’s head of fundraising, said: “We are so grateful to Phyll for undertaking this typically gutsy fundraising project in her 100th year.
“Our charity does not receive any financial support from central or local government and so we are very much dependant on the generosity of the public in Wiltshire and further afield.”
No stranger to challenges, Ms Babb, who was born in Bideford, north Devon, travelled by sea alone to Jamaica in 1949, where she taught in a girl’s grammar school for three years.
After a brief spell in England, she took off again to Vancouver in western Canada before returning to the UK to look after her disabled mother.
She was also a keen member of the local yacht club before retiring in 1986 and then taking on a range of volunteering opportunities.
To donate to STFH please click here: https://www.justgiving.com/page/phyll-babb-1722779310016