The sale of GMG Regional Media by Guardian Media Group will see Trinity Mirror take control of 32 newspapers published by its two subsidiary companies, MEN Media and S&B Media.
The deal, which is due to be completed on 28 March, will see Trinity Mirror make a payment of £7.4 on completion with a further £37.4m coming from GMG being released from its long term printing contract with Trinity Mirror.
Carolyn McCall, chief executive of Guardian Media Group, said today the deal delivered "real value for both parties".
McCall again stressed how GMG was mandated to "secure the future of the Guardian in perpetuity" saying that the group's portfolio of businesses had to be "in the right shape to achieve that goal".
She said: "The group board and the Scott Trust have made the decision to sell in light of these strategic objectives.
"GMG Regional Media is a good business and a publisher of important newspapers. However, we believe Trinity Mirror, as the UK's biggest regional publisher, is best placed to develop this business."
News of the deal follows GMG confirming in December that it has held "exploratory talks" with rivals about selling the Manchester Evening News and its other regional newspapers.
Mark Dodson, chief executive of GMG Regional Media, will now leave the company along with Ruth Spratt, managing director of MEN Media.
David Sharrock, currently chief operating officer of GMG Regional Media, has been appointed as managing director of MEN Media.
MEN Media currently produces 22 titles in and around Greater Manchester, including flagship title the Manchester Evening News.
Despite the change of ownership the business will operate as a stand-alone subsidiary in Trinity Mirror's regional newspaper operation rather than being taken under the control of its North West division.
S&B Media publishes 10 titles in the South of England, including the Surrey Advertiser and Reading Post. This business will now come under the control of Trinity Mirror's southern division.
Confirming its takeover today, Trinity Mirror said it would not be acquiring Channel M, the GMG TV station which serves Greater Manchester, and two local newspapers in Woking - raising fears that these outlets could now close.
Sly Bailey, chief executive, of Trinity Mirror, said: "GMG Regional Media is a perfect strategic fit for our group.
"This acquisition, which includes the Manchester Evening News with its proud and rich journalistic heritage, together with the weekly titles and associated websites extends our reach across print and online and is a further step towards our strategic goal of creating a multi-media business of real scale."
Oliver Luft writes for Press Gazette