Mary Hampton's bicycle was taken while she did her weekly shop in Waitrose.
The 89-year-old from Berkhamsted in Hertfordshire admitted she was "very silly" not to have locked it, but in 85 years of cycling she "never had".
After news of the theft hit social media, dozens offered to buy Mary a new one. Her local cycling club has loaned her one "for as long as I need it".
Mrs Hampton was in the habit of cycling the three miles to the supermarket once or twice a week on her trusty Raleigh Shopper.
But when she went shopping last Thursday, she returned to find her bike gone.
The former primary school teacher said: "It was an old-looking bike, I didn't think anybody would be going to steal it."
Her plight was shared on social media and within 24 hours, dozens of offers of new bicycles flooded in for Mary via Facebook.
She finally accepted a loan of a fold-up bicycle from Berkhamsted Cycling Club.
People also clubbed together to give her money for a new lock and a basket for her new bike.
"I've bought a huge padlock. I've never seen such a big padlock," Mrs Hampton said.
"One bad action happened, but think of the wonderful kindness and caring that's come from it," she added.

The Academies Enterprise Trust (AET), which runs Weston Academy, said it made the "sad decision", due to falling pupil numbers.
The 56-pupil school was classed as "inadequate" by Ofsted in March.
A petition set up by parent George Metcalf, describing closing the school as a "huge waste of resources" attracted more than 500 signatures.
The campaign won the backing of the National Secular Society as parents claimed the nearest alternatives were all faith schools.
The school was placed in special measures following an Ofsted report in March which criticised leadership and management, pupils' behaviour, the quality of teaching and achievement of pupils.
But in May the watchdog reported that teaching and leadership was improving.
AET said the school had less than 40 pupils and the Department for Education had confirmed its agreement to closing the school at the end of December.
Chief executive Ian Comfort said: "Closing a small school is always a very sad decision to make, and is only taken as a very last resort.
"The declining numbers at Weston, however, have been making it increasingly difficult for the school to provide pupils with the quality of education they deserve. I am sure they will all thrive in their new schools and we wish them, and the staff, every success in the future."

Dorothy Leyden's body was found hours after she had been to a Jimmy Ruffin concert at the Golden Garter nightclub in Wythenshawe in April 1971.
The 17-year-old's body was found on waste ground in Collyhurst.
Her sister Pat Atkinson has made an emotional appeal for more information on her death.
The teenager spent the evening of 24 April 1971 at the concert before heading into central Manchester.
At about 02:30, she got out of a taxi she had shared with friends at Piccadilly Gardens bus station and it is thought she decided to walk home.
Her body was found the following day behind the now demolished Spread Eagle pub.
A reconstruction will show some of Dorothy's last known movements before she was attacked.
Previously, it had been thought she may have been murdered by serial killer Trevor Hardy but, this was dismissed in 2008.
Det Supt Martin Bottomley, from Greater Manchester Police, said forensic evidence proved he did not kill Dorothy.
"The suspicion that Hardy was responsible may have allowed the real killer to hide for all of this time."
Dorothy's sister recalled the moment officers broke the news of her sister's murder.
She told Crimewatch: "I remember the police coming to the front door and I just went out playing and when I came home my mum called me into the living room.
"I think she told us all one at a time and she just told me that Dorothy had been beaten and she'd died."
The appeal will be shown on Crimewatch later on BBC One at 21:00 BST.
An elderly woman whose bicycle was stolen while she was shopping has been overwhelmed by offers of replacements.
[NEXT_CONCEPT]
An Isle of Wight primary school is to close, despite a parents' campaign to keep it open.
[NEXT_CONCEPT]
A fresh appeal to find the killer of a teenage girl who was raped and murdered in Manchester 45 years ago is to feature on BBC One's Crimewatch.