Queensland Police Service Commissioner Steve Gollschewski advised he would take leave on Friday, with Premier David Crisafulli saying he had the government's full support.
"Right now, his focus must be on his health and his family - but on behalf of Queensland - I want to thank him for his outstanding contribution to the state and wish him all the best on his journey ahead," Mr Crisafulli said in a statement.
Deputy Commissioner Shane Chelepy will serve as acting commissioner from Saturday.
Police Minister Dan Purdie said Mr Chelepy would ensure strong and stable leadership of the force continued.
In a letter issued to his officers on Friday, Mr Gollschewski said he looked forward to his recovery and returning to finish the work they'd started, according to Brisbane newspaper, The Courier Mail.Â
"It is with great disappointment I have to advise you that I have commenced leave for an unknown period following an unexpected cancer diagnosis," it said.
"I have a battle ahead of me and with the support of my family need to concentrate my energies towards my treatment."
Mr Gollschewski was officially appointed commissioner in April 2024, having acted in the role after predecessor Katarina Carroll announced she would not seek an extension in the position in February.
He stands down a year to the day Ms Carroll departed.
A career officer, Mr Gollschewski has spent more than four decades in the Queensland Police Service after joining in 1980. His career path included more than 10 years as deputy commissioner before assuming the top job.
Mr Gollschewski led the state's response to the COVID-19 pandemic, overseeing hotel quarantine and border security.
He also oversaw security for the 2018 Commonwealth Games on the Gold Coast and co-ordinated the state's response efforts for numerous floods and cyclones.
He was awarded an Australian Policing Medal in 2010.
