The Barclay brothers have agreed to sell The Scotsman newspaper and other titles to Johnston Press in a deal worth £160m.
The Scotsman describes itself as "Scotland's national newspaper"
The sale includes the Edinburgh Evening News, Scotland on Sunday and the free Edinburgh Herald & Post.
Twins David and Frederick Barclay also own the Telegraph Group through their Press Holdings Group, which in turn owns The Scotsman Publications Ltd.
Johnston Press has agreed to acquire its entire issued share capital.
The company is the fourth largest publisher of local and regional newspapers in the UK.
Scotsman Publications has a total weekly paid-for circulation of 840,000 and a weekly free distribution of 254,000.
Its website, scotsman.com, registered more than three million unique users and more than 20 million page impressions in its most recent ABC audit.
In the last financial year ended 31 December 2004, Scotsman Publications reported profit before interest and tax of £7.7m on turnover of £63.5m.
Johnston chief executive Tim Bowdler said: "Scotsman Publications comprises one of Scotland's highest quality newspaper portfolios and The Scotsman and its website scotsman.com are amongst Scotland's best known newspaper and internet brands.
"With its Scottish heritage, Johnston Press is particularly pleased to have reached agreement to acquire Scotsman Publications."
Andrew Neil, publisher of the Press Holdings Group, owners of The Scotsman Publications Limited (TSPL), said: "It has been a privilege to own and run a prestigious flagship title like The Scotsman, along with its successful associated titles, these past 10 years.
"But we are delighted to have reached an agreement with Johnston Press which not only recognises the value and improvements we have added to the titles over the decade but secures their long-term future.
"The Scotsman and its sister papers will now have the advantage of being part of a larger Edinburgh-based group."
Some of the 250 journalists employed on the newspapers expressed unease following the announcement.
The website has registered more than three million unique users
One told the BBC Scotland news website: "Everyone was shocked, they were all taken into a room and told the news.
"There is a feeling of uncertainty and everyone's a little bit scared. There are a lot of perplexed looking faces.
"People are worrying because when new people take over there is usually cost-cutting, so everyone's concerned for their jobs."
However, another staff member who had worked on a publication which was taken over by Johnston Press, said that had been a "good thing".
He said: "They are an Edinburgh family and it would be very embarrassing if they ruined Scotsman Publications."
There was speculation that some of Johnston Press's local newspaper operations would be moved into The Scotsman building in Edinburgh.
The Barclay Brothers bought the company eight years ago for £87m but The Scotsman has been losing circulation in recent years with a daily sale of 59,000 last month.
The acquisition will add The Scotsman to a growing list of newspaper titles owned by Johnston Press.
Earlier this year, Johnston Press spent £155m on Scottish Radio Holdings' newspaper arm, Score Press.
Alex Salmond, the leader of the Scottish National Party, welcomed news of the sale.
"Johnston Press has an excellent reputation in terms of the papers in their stable, while conversely The Scotsman had a poor period under the previous owners," he said.
"Hopefully this is a positive step into the future for important Scottish titles."