Dairy Crest, whose brands include Cathedral City cheddar and Country Life butter, has agreed to be bought by a Canadian company in a near-£1bn deal.
Saputo, one of the biggest dairy processors in the world, will pay 620p a share, valuing Dairy Crest at £975m.
The deal is Saputo's first in Europe and it said Dairy Crest was an "attractive platform" for UK growth.
Dairy Crest said "virtually" all its 1,100 UK jobs are safe, including 150 at its head office in Surrey.
However, the Unite union said it would be "seeking an urgent meeting" with Saputo about assurances over job security.
Dairy Crest's share price, which has risen steadily this week, had jumped almost 12% in late morning trading on Friday.
Saputo has expanded rapidly in recent years through acquisitions. In 2017, the company bought Australia's Murray Goulburn Co-operative for $490m (£380m), becoming the country biggest milk producer. Saputo has also expanded into China.
It said its interest in Dairy Crest had been motivated by a desire to increase its international presence and "enter the UK market by acquiring and investing in a well-established and successful industry player".
The Canadian company said that, under its ownership, Dairy Crest would continue to manufacture its products from its existing UK facilities, and that it also intended the management of its UK operations to remain in Surrey.
Dairy Crest's brands
- Cathedral City cheese
- Davidstow cheese
- Country Life butter
- Utterly Butterly
Saputo chairman and chief executive Lino Saputo Jr said: "We believe that under Saputo ownership, Dairy Crest will be able to accelerate its long-term growth and business development potential and provide benefits to Dairy Crest's employees and stakeholders."
Dairy Crest's board has unanimously recommended that shareholders accept Saputo's offer.
The chairman of Dairy Crest, Stephen Alexander, said: "The acquisition should enable Dairy Crest to benefit from Saputo's global expertise and strong financial position to fulfil and accelerate its growth ambitions.
"The businesses have strong shared values and the board is confident that Saputo's plans to invest in and grow the Dairy Crest business mean the proposed transaction is positive for all its stakeholders."