Sainsbury's J Sainsbury plc () is the parent company of Sainsbury's Supermarkets Ltd, commonly known as Sainsbury's (also Sainsbury and JS), the third largest chain of supermarkets in the United Kingdom with a share of the UK supermarket sector of 16.3%. The group also has interests in property and banking.Sainsbury's was founded in 1869 by John James Sainsbury and his wife Mary Ann (née Staples), in London, England, and grew rapidly during the Victorian era.