Pub group Marston's is to take over the running of 156 S.A Brains pubs in Wales in a move expected to safeguard 1,300 jobs.
Brains' chairman John Rhys said the decision had not been taken lightly but would allow the company to continue "for generations to come".
Brains, founded in 1882, is Wales' largest domestic pub chain and runs the heritage beer brand of the same name.
Marston's will operate the Brains pubs on a combination of leased and management contract arrangements. They will continue to trade under the Brains brand to serve its beer.
The company said Covid restrictions in Wales had put Brains under significant financial pressure, so it had entered collaborative discussions to preserve the brand and secure jobs.
Welsh hospitality was ordered to close on 19 December, but 100 of Brains' managed pubs have been closed since 4 December when a ban on serving alcohol across Wales came into force.
The deal will add to the existing 106 Marston's pubs in Wales.
Marston's will operate the 141 Brains freehold pubs on a leasehold basis from February 2021. The outlet level earnings before interest, taxes, depreciation, and amortisation pre-Covid was £14m and annual rent of £5.5m will be charged from April 2021
Marston's will also operate 15 short-leasehold sites on management contracts for two years.
Ralph Findlay, chief executive of Marston's, said: "This transaction is entirely consistent with Marston's long-term strategy as a focused pub operator and strengthens our representation in south and west Wales, while protecting the heritage and independence of an iconic Welsh business.
"These high-quality pubs are a great fit with our existing estate and will benefit from Marston's scale and operational expertise to further unlock their excellent long-term potential.
"We look forward to the pub teams joining us and to welcoming guests and the communities which they serve back into these pubs as the country emerges from the pandemic over the weeks and months ahead."
Marston's expects the deal to be earnings accretive within the first year and sees opportunities for further growth and investment in the estate.
The deal is expected to complete in February 2021.