The Irish Times has agreed to acquire the "publishing and media interests" of the company that owns The Irish Examiner.
As well as the Examiner, Landmark Media owns a range of local newspapers - such as the Evening Echo, Waterford News and Star, Western People, and The Nationalist.
The company also has majority stakes in radio stations WLR in Waterford and the south-east regional station Beat, and operates the news website BreakingNews.ie.
The Irish Times says a share purchase agreement was signed yesterday.
While the deal has been agreed between the two companies, it will need to be approved by the Competition and Consumer Protection Commission, the Communications Minister, and the Broadcasting Authority of Ireland (BAI).
The process is expected to take up to six months to complete.
Liam Kavanagh, managing director of The Irish Times, said: “We don’t underestimate the challenges ahead but this combination could underpin the future of two long-standing, Irish-owned media organisations…that are like-minded editorially.”
Landmark Media Investments Group CEO Tom Murphy added: "For our part, we believe we have done everything possible to make and implement the right decisions in relation to the Landmark business and all of its stakeholders, particularly our very valued and loyal staff colleagues.
"I believe that a sale of the Landmark Media business to The Irish Times is in the best interest of all of the stakeholders, including staff, in Landmark Media and that it is the correct outcome also for The Irish Times and the Newspaper and Media industry generally in Ireland."