Mr Gilson had been a surprise appointment to the job
The editor of The Scotsman newspaper has resigned from his post after just over two years in charge.
Mike Gilson, 45, who had been an editor of Johnston Press titles for more than 12 years, was a surprise appointment to the job in September 2006.
The Edinburgh-based newspaper confirmed his departure on Thursday night.
Edinburgh Evening News editor John McLellan is expected to take over as his successor in The Scotsman editor's chair on Monday.
Mr McLellan will become title's 10th editor since Magnus Linklater left in 1994.
There has been speculation that owners Johnston Press could restructure The Scotsman and sister titles Scotland on Sunday and the Edinburgh Evening News.
In a brief statement, The Scotsman managing director Michael Johnston said Mr Gilson had "relinquished his position with immediate effect".
He added: "Further announcements will be made in due course. The company has no other comment to make at this time."
Mr Gilson was previously editor of The News in Portsmouth from 2000, and had also worked as editor of the Peterborough Evening Telegraph, night editor of The Western Mail in Cardiff, and news editor of the Hull Daily Mail.
The Scotsman's circulation has fallen to about 50,000 copies a day under his stewardship - its lowest in modern times.
Scotland on Sunday editor Les Snowdon left his post earlier this month to become sports editor of the Daily Mail and has not yet been replaced.
Mr Snowdon and Mr Gilson had been appointed to their jobs just three weeks apart.
At the time, Mr Johnston said: "Their appointments underscore Johnston Press' commitment to The Scotsman and Scotland on Sunday's future as the nation's leading quality newspapers."