Morrisons has agreed to sell 18 Safeway stores and one from its own chain in Southport, Lancashire.
Waitrose said the deal would take it into new territories in the North of England and Wales and strengthens its presence in the South.
Managing director of Waitrose, Steven Esom, said the move would bring “fresh competition and new levels of choice for customers in these new trading areas”.
The stores will continue to be operated by Morrisons until they are converted to the Waitrose fascia “over the coming months” and to be completed in time for Christmas trading, said Waitrose.
The sale of 14 of the stores by the enlarged Morrisons group is to satisfy competition concerns. Morrisons said it had elected to sell its store in Southport rather than the Safeway outlet in the town.
Waitrose noted that the stores acquired would add over 500 million sq ft of selling space to its existing 144 estate.