Don Choco is being rolled out into Spar stores and wholesalers including Dhamecha, JW Filshill and CJ Lang, in a 100g bar retailing at £1.
The launch is supported by a campaign across Facebook and Instagram.
Ritter Sport says darker and higher cocoa content chocolate is growing 9% year on year and so this new bar is expected to help drive incremental category sales.
Katy Clark, head of marketing at Ritter Sport, said: “Sustainability is already on trend, and dark milk has a strong appeal for shoppers wanting to try darker and higher cocoa content chocolate and so this delicious new bar, made from 100% certified, sustainable cocoa, is set to be a win-win with consumers and retailers alike.”