The long-running publication was launched in November 1972 by founding editor Ita Buttrose and media mogul Kerry Packer.
It has since been edited by prominent female media personalities including Lisa Wilkinson, Deborah Thomas and Mia Freedman.
"It's very sad to think a magazine has come to an end, as it has obviously played an important part of my life and I'm very proud of it," Buttrose told AAP on Wednesday.
"It taught me a lot about running a team, it taught me how to be bold, and it enabled me to ultimately take on the Women's Weekly and the Consolidated Press."
Cleo, she said, was "her first big success" and offered up something new to its audiences at the time.
"It coincided with women's liberation, with women wanting to have careers as well as marriage and motherhood," she said.
Buttrose made her mark on the industry when she introduced the nude male centrefold in the launch issue, with Aussie actor Jack Thompson being the first to strip down for Cleo.
A little more than a decade later, Wilkinson took the reigns and scrapped the nude dudes altogether, replacing them with the now-famed annual list of Cleo's 50 Most Eligible Bachelors.
A move she said was the best statement she could make that Cleo "so linked to its '70s birthplace, had moved on, into the go-ahead '80s".
The now TV personality and HuffPost Australia editor-at-large took to the web to farewell Cleo.
"It seems extraordinary that this once-thriving publication ... will no longer be that wise, informed, supportive friend to the legions who once so eagerly bought and devoured its pages each month," she wrote in a HuffPost Australia column.
"You were fun, informative, lusty and liberating, and several generations of Australian women are in your debt.
"We will miss you."
Bauer Media also confirmed plans to relaunch Cleo's stablemate Dolly with a greater focus on the online market.
"And just like that as CLEO's closure is confirmed, DOLLY as we knew it, is gone too. Sad on so many levels. Vale." Wilkinson tweeted on Wednesday.
- Additional reporting: AAP