The owner of the Daily Mirror has agreed to buy the company behind titles including the Daily Express, the Daily Star and magazines such as OK!
The deal is subject to shareholder approval.
Trinity Mirror is to pay £126.7m for the publishing assets of Northern & Shell, which is owned by Richard Desmond.
Sale talks were announced in September, but a deal between the two has been on the cards for some time.
The sale brings to an end Mr Desmond’s 18 years as a UK newspaper owner.
Northern & Shell’s publishing assets include the Daily Express, Sunday Express, Daily Star and Daily Star Sunday, as well as three celebrity magazines, OK!, New! and Star.
Simon Fox, chief executive of Trinity Mirror, said: “Northern & Shell’s titles have a large and loyal readership, a growing digital presence and a stable revenue mix and offer an excellent fit with Trinity Mirror.”
Speaking to the BBC’s Today programme, he said: “It’s a very wise investment. We’ve had plenty of time to think about this carefully.”
He said the deal would lead to cost savings, as the titles could pool their resources. “For example, [instead of] sending two reporters to a football game, we can send one.” Trinity Mirror expects the deal to lead to savings of £20m a year.
Mr Fox pledged that the publications would retain their identities: “The Daily Express is not going to become left-wing and the Mirror is not going to become right-wing.”
