David Kirk has stepped down as chief executive of Fairfax Media after three years in the job.
Fairfax chairman Ronald Walker announced the resignation on Friday but provided no explanation for the move, which is effective immediately.
Deputy chief executive Brian McCarthy will act as interim chief until the board meets next Wednesday.
Mr Walker said some of the highlights of Mr Kirk's time as chief included the Fairfax merger with Rural Press and the rapid growth in internet earnings.
Mr Kirk said it had been a privilege to lead Fairfax Media during what he called a period of great change and challenge for media companies all over the world.
Fairfax Media is the publisher of The Age and Sydney Morning Herald, as well as The Dominion Post, Sunday Star-Times, The Press and The Waikato Times in New Zealand. It also owns the Trade Me website.
Mr Kirk took over as Fairfax chief executive in November 2005, replacing Fred Hilmer at the end of his seven-year reign.
The former All Blacks rugby captain came to Fairfax from PMP Limited, a printing and media services company.
Mr Kirk oversaw turbulent times at Fairfax, including the merger with Rural Press, a tumbling share price amid concerns about the newspaper industry, and widespread job cuts.