Christina Mackenzie, from Stirling, cycled the gruelling 839-mile-long route in just 51 hours, five minutes and five seconds.
The 44-year-old’s achievement breaks the previous record, of 52 hours, 45 minutes and 11 seconds, held by Lynne Taylor since October, 2002.
The Falkirk Community Trust swimming development officer set off from the southernmost tip of Great Britain at 8am on Wednesday, finishing at 11:05am on Friday.
She was already recognised as the fastest Scot, and the third fastest woman in the world, to complete the epic endurance race – known as LeJog – after finishing it in 2019 with a time of 55 hours, 17 minutes and 19 seconds.
Gary Hand, Ms Mackenzie’s trainer at Espresso Cycle Coaching, said that while it took time to build her confidence up after she lost the record pace in the last quarter of the race back in 2019, she has a “tremendous work ethic.”
He said: “It began with a breakdown of the first attempt, finding out in detail what was good and what could have been improved.
"From there, I got to work. We optimised her bike position… and we dropped 9kg in weight.
"The danger there is in losing power, but we increased in wattage output also across the important power bands.”
He continued: "Christina has a tremendous work ethic and is not scared of pain.
"Going into Friday, we knew Christina's confidence was high. We knew we had done everything possible in preparation.
"We studied the wind and knew the day to go for it. From there it was down to Christina to push the pedals, eat and listen to her team.
"She's tough and there are only certain human beings that can take themselves to these depths of fatigue - and with her huge mental strength she is one of them."
Neil Brown, General Manager, Falkirk Community Trust said “Everyone at Falkirk Community Trust is immensely proud of Christina’s achievement.
“We have been following Christina’s progress since she began her journey and knowing the hard training and preparations that she had undertaken over a number of years, she thoroughly deserves to be the new record holder.”
Ms Mackenzie, who previously won the 2020 Veterans Time Trials Association (VTTA) 12 hour national championship, has so far raised more than £7,600 for Alzheimer Scotland with her latest cycling feat.
Commenting on Ms Mackenzie’s achievement, James McCallum, Scottish Cycling board member and Commonwealth Games representative, said: “Congratulations to Christina, from everyone at Scottish Cycling, on a remarkable achievement.
"Preparing for and executing a long distance record attempt takes a small army to achieve, so hats off to her and her support team.”
A Spokesperson from Duncan Mackay and Sons Ltd, one of Ms Mackenzie's sponsors said: "We are delighted with the news that Christina broke the female record for cycling LeJog.
"Hector and Buddy [company directors] know Christina through cycling, being amateur cyclists themselves, so were excited to sponsor her and were rooting for her all the way.
"Both recognise how tough this challenge was but never expected her to break the record by such a monumental time!
“It's a proud day here at Duncan Mackay and Sons Ltd."
You can donate to Ms Mackenzie’s latest fundraising effort here.