Bridie O'Donnell's contentious appointment as a Collingwood board member has lasted only four months, with work commitments forcing her to leave the drama-plagued AFL club.
The former world record-breaking cyclist was among four board members who were up for election ahead of the December 16 club annual general meeting.
O'Donnell announced on Thursday she was stepping down because of her new role as an area controller in Victoria's COVID-19 outbreak response team.
It is understood she informed the board early on Wednesday evening.
Also on Wednesday night, she was criticised for a weekend Instagram post that showed support for the Western Bulldogs in their preliminary final against Port Adelaide.
Former Magpies president Eddie McGuire said on Channel Nine the post was "ill-advised".
O'Donnell's bona fides as a Collingwood fan and her eligibility to serve on the board were questioned when she was appointed to the board in May as a casual vacancy.
Her resignation adds to the off-field turmoil at Collingwood, with Jeff Browne challenging for the presidency.
Current president Mark Korda confirmed earlier this month he would step down as a director at the end of next season.
In her statement, O'Donnell said she took on the new work role last week and it quickly became clear it would require all her attention.
"When I had the privilege of accepting a position on the board of Collingwood four months ago, I had no comprehension that I would be taking on a task of this magnitude in September," she said.
"I considered over the last few days that I might request a period of leave from the board, but I'm aware that there are so many important pieces of work underway which require the group's full commitment.
"Consequently, I will step down from my role as ex officio board director, effective immediately."