Tesco has submitted proposals to build both Extra and Metro formats in the Kent town, claiming they will create more than 500 jobs for local people.
Morrisons, meanwhile, has signed up to be the centrepiece store at a proposed mixed development scheme, including 200 new homes, on the site of a former paper mill.
The retailer, which claims its proposed 72,000 sq ft store will create up to 400 jobs, is hoping to use the scheme as part of its mission to grow its presence in the south east.
If both these applications are successful, Sittingbourne, which has a population of 45,000, will be one of the best serviced towns in the country for supermarkets as Asda, Sainsbury's and Aldi already have stores there.
However, Tesco claimed its plans, which include proposals to redevelop the town centre's shopping and leisure facilities, would also keep money in the town. "More than 70% of local shopping trips are currently outside Sittingbourne and we wish to reverse this trend," said Jonathan Simpson, Tesco's corporate affairs manager.
Morrisons already has a presence in Sittingbourne, having opened a 1 million sq ft distribution centre in the town a year ago to service its expansion plans in the south east, and creating 952 new jobs in the process.