The woman, 74, was on the hard shoulder cycling between junction 10 for Cobham and junction 11 for Chertsey.
Police said she was seen earlier using the motorway as a shortcut at about 14:20 BST, Surrey Police said.
A spokesman said the woman, from New Haw, was given a fixed penalty notice and "words of advice" before her bike was put in the back of a patrol car.
She was then taken to another road to continue her journey.
A cyclist found using a section of the M25 as a shortcut, has been stopped by police.