South Africa's Spar Group is to buy an 80% stake in BWG Group, which owns Spar in Ireland and the southwest of England, for €55m.
The company said the acquisition would give Spar a "well-positioned international retail platform for future expansion".
BWG operates more than 1,100 stores around the country with annual revenues of €1.2 billion. Its brands here include Spar, EuroSpar, Mace, ValueCentre and XL and it has 35% of the Irish convenience store market.
It employs about 1,000 people directly and about 20,000 people in its stores, including owner-run franchise outlets.
The South African company said it decided on the deal due to its compelling long-term return expectations, while the deal was also underpinned by the "positive economic fundamentals in Ireland".
BWG will continue to be led by its group CEO Leo Crawford and the existing management team and the company said there will be no change to the structure or composition of the existing businesses.
The new partnership will have up to €100m to invest in the expansion of the wholesale and convenience retailing operations over the next five years.
BWG and Spar South Africa are well known to each other as both have been members of Spar International for the last 50 years. Mr Crawford is currently chairman of Spar International.
The company's CEO Leo Crawford said the move was a very positive and exciting development for it.
"In Spar South Africa, we have secured a major international retail player as a strategic partner and a long term investor in our business. We look forward to working with their team to accelerate the expansion of our operations and the growth of our wholesale and retail businesses in Ireland and the south west of England," he added.
BWG was originally part of the Brooks Watson Group before being acquired by Irish Distillers in the 1980s. The company was then bought from French drinks company Pernod Ricard in 2002 after a management buy-out - led by Leo Crawford - which was supported by Electra Partners, the London based venture capital company.
In 2006, Triode Investments, a company controlled by Mr Crawford, John Clohisey and John O'Donnell completed the purchase of BWG Group from Electra.
Spar South Africa has a turnover of about €3.5 billion and a stock market value of about €1.5 billion. Its brands there include Superspar, Spar, Kwikspar and SaveMor supermarkets.