Mavis Paterson, who was widowed in 1996, saw her son and daughter die from health problems just six months apart in 2012 and 2013, then lost her other son in an accident three years ago.
Now the heartbroken Scottish octogenarian, from Auchenmalg in Wigtownshire, plans to pedal 960 miles from Land’s End to John O’Groats in their memory.
Along the way she also hopes to raise £20,000 for the charity Macmillan Cancer Support, which she began backing after her mum and younger sister died from the disease.
The Guinness Book of Records has confirmed Mrs Paterson will be the official record holder once she completes the route.
“I’m excited and a little bit nervous about getting started, however it’s something I really want to do,” she said.
“It will be nice to get the world record, but for me I’m doing it to raise money for Macmillan and because cycling and taking on big challenges help me cope with the unimaginable grief of losing my children.
“It’s impossibly hard going from being part of a family of five to being alone, but it’s taking on challenges like this that keep me going, and I’m happy I can do it to raise money for Macmillan.
“I’ve taken on big challenges before, but this will be the toughest.”
It is not the first time the pensioner, who has three grandchildren, has got on her bike to raise funds for the charity.
Last year she completed a 24-hour cycle in the west of Scotland and ten years ago rode across Canada.
Derek Watson, fundraising manager for Macmillan, said: “Mavis is incredible. The challenge she has set herself is astounding and we cannot wait to cheer her on to get that world record.
“Her determination, incredible level of fitness and her generosity is astounding.”
Alex Menarry, from Darlington, became the oldest man to cycle the route last year when he completed the trip at the age of 85 and 291 days.
Mrs Paterson will begin the epic journey on 24 May and aims to complete it in three weeks, reaching John O’Groats on 13 June.
Sustenance is being provided by a special Tunnock’s camper van stocked with teacakes and caramel wafers.