The Channel 4 show, which pushes recruits to their mental and physical limits in a series of gruelling military-style tests, will continue without Ollerton and co-star Jay Morton as part of the instructor line-up.
The broadcaster said Ollerton had stepped away from the role to focus on his fitness app, Battle Ready 360, but would continue to be associated with the Australian version of the programme.
Ollerton has filmed five series of SAS: Who Dares wins, plus two series of the celebrity spin-off version.
Morton will also leave the show after featuring in its most recent civilian and celebrity series, debuting as an undercover agent embedded within the recruits.
Ollerton appeared to allude to the development on Instagram on Monday.
In a post to his 348,000 followers, he said that “comfort zones can be dangerous places to reside”.
“There’s no real comfort, just habit that is comfortable to repeat. You sit within it going through the motions which can be like a life long tooth ache.
“A simple extraction pushes you into short term discomfort but in turn offers you a new path with no pain.
“A place where you have the bandwidth for creativity and development.
“When this happens in your job, your relationship, your life, ask yourself if the internal messaging reflected your desire for its continuation.
“If it didn’t then this is the death of something that didn’t serve you well, and the subsequent start of something exciting and new.”
He concluded: “Embrace it, exploit it, enjoy it.”
A Channel 4 spokeswoman said of his departure: “Planning for series six of SAS: Who Dares Wins is under way, with strict safety measures and protocols in place to ensure a safe filming environment, in line with government advice.
“Now in its sixth year of filming, some changes have been made.
“Ollie Ollerton has stepped away from this series after a hugely successful seven series with the show to focus on his new fitness app, Battle Ready 360.
“Ollie continues to be associated with the SAS: Who Dares Wins brand as a DS (directing staff) for SAS: Who Dares Wins Australia.
“Ollie has made an exceptional contribution to SAS: Who Dares Wins and the expertise and experience he brought to the DS team has been much valued.
“We wish him great success with his future projects.”
She said of Morton: “Jay joined the latest civilian series of SAS: Who Dares Wins, working undercover for the DS, before joining the team for the remainder of both the civilian and celebrity series.
“With his unique Special Forces experience he made a valuable contribution to the series.”
The statement added: “We will be announcing the new line-up in due course.”
Ollerton, a former special forces soldier, has been an instructor on the show since it first aired in 2015, initially working alongside Ant Middleton and Jason Fox.
He has published a number of books including Battle Ready and Break Point, about his experiences of depression and substance abuse, and launched a fitness app called Battle Ready 360.
