Brewery, whose bottled beers include Ringwood Best, Old Thumper, Boondoggle , the bottle-conditioned Fortyniner and XXXX Porter.
The brewery paid £19.2 million for Ringwood, including seven freehold pubs. It said it would continue brewing all Ringwood's brands
and use the brewery as a base for its operations in the region.
Managing director Alistair Darby said: "We are delighted to welcome Ringwood to Marston's. We plan to develop its excellent brands as part of our strategy to meet consumer demand for premium ales with local provenance and heritage. Our premium ale business continues to deliver good, consistent growth and we look forward to replicating the success of the Jennings business through Ringwood in the south of England."
The Campaign for Real Ale warned that the buyout could spark a domino effect and see more larger breweries buying up smaller competitors.
Chief executive Mike Benner said: "The practice is a race where the only loser is the consumer, who is often denied a locally brewed beer.
"Marston's purchased Jennings in Cumbria and invested in the future of the brewery
- and we hope they will continue this model with Ringwood."
The Society of Independent Brewers, of which Ringwood was a founding member, reacted with mixed feelings. Chairman Peter Amor said small breweries are becoming more successful
and that is attracting the attention of bigger competitors who then snap them up, either to invest in them or to close them down.
"We hope that Marston's will stand by their promise to keep the brewery running," he said.